Điều kiên: x≤2∨x≥10" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">x≤2∨x≥10x≤2∨x≥10Đặt {a=x2−7x+10b=x2−12x+20⇒2a−b=x" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">{a=√x2−7x+10b=√x2−12x+20⇒2a−b=x{a=x2−7x+10b=x2−12x+20⇒2a−b=xPT⇔2[x2−7x+10−(x+1)]=x2−12x+20−(x+2)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">PT⇔2[√x2−7x+10−(x+1)]=√x2−12x+20−(x+2)PT⇔2[x2−7x+10−(x+1)]=x2−12x+20−(x+2)2[(x2−7x+10)−(x+1)2]x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2x2−12x+20+(x+2)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">2[(x2−7x+10)−(x+1)2]√x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2√x2−12x+20+(x+2)2[(x2−7x+10)−(x+1)2]x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2x2−12x+20+(x+2)⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2Xét phuơng trình 18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1)18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1) (#)Kết hợp với đầu bài, 2a−b=x⇒b=2a−x" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">2a−b=x⇒b=2a−x2a−b=x⇒b=2a−x(#) viết lại là 5x2−7x+10=4x−5⇔x=15±552" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">5√x2−7x+10=4x−5⇔x=15±5√525x2−7x+10=4x−5⇔x=15±552Thử lại chỉ thấy nghiệm x=15+552" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">x=15+5√52x=15+552 là thỏa mãn.S=1;15+552" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">S=1;15+5√52S=1;15+552
Bài này có ng đã đăng r:Nhấn vô đây xem lời giải.
Điều kiên: x≤2∨x≥10" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">x≤2∨x≥10x≤2∨x≥10Đặt {a=x2−7x+10b=x2−12x+20⇒2a−b=x" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">{a=√x2−7x+10b=√x2−12x+20⇒2a−b=x{a=x2−7x+10b=x2−12x+20⇒2a−b=xPT⇔2[x2−7x+10−(x+1)]=x2−12x+20−(x+2)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">PT⇔2[√x2−7x+10−(x+1)]=√x2−12x+20−(x+2)PT⇔2[x2−7x+10−(x+1)]=x2−12x+20−(x+2)2[(x2−7x+10)−(x+1)2]x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2x2−12x+20+(x+2)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">2[(x2−7x+10)−(x+1)2]√x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2√x2−12x+20+(x+2)2[(x2−7x+10)−(x+1)2]x2−7x+10+(x+1)=(x2−12x+20)−(x+2)2x2−12x+20+(x+2)⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2⇔−(x−1)(18a+x+1−16b+x+2)=0⇔x=1∨18a+x+1=16b+x+2Xét phuơng trình 18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1)" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1)18a+x+1=16b+x+2⇔9(b+x+2)=8(a+x+1) (#)Kết hợp với đầu bài , 2a−b=x⇒b=2a−x" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: n one; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">2a−b=x⇒b=2a−x2a−b=x⇒b=2a−x(#) viết lại là 5x2−7x+10=4x−5⇔x=15±552" role="presentation" sty le="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-bloc k; lin e-heig ht: 0; word-wrap: n ormal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-heig ht: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">5√x2−7x+10=4x−5⇔x=15±5√525x2−7x+10=4x−5⇔x=15±552Thử lại chỉ thấ y n ghiệm x=15+552" role="presentation" style="padding-top: 1px; padding-bottom: 1px; font-size: 16.38px; display: inline-block; line-height: 0; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; color: rgb(40, 40, 40); font-family: helv etica, arial, sans-serif; position: relative; background-color: rgb(255, 255, 255);">x=15+5√52x=15+552 là thỏa mãn.S=1;15+552" role="presentation" sty le="padding-top: 1px ; padding-bottom: 1px; font-size : 16.38px; display: inline-block; line-height: 0; word-wrap: norm al; white-space: nowrap; fl oat: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-hei ght: 0px; color: rg b(40, 40, 40); font-fami ly: helvetica, arial, sans-serif; positi on: relative; background-color: rgb(255, 255, 255);">S=1;15+5√52S=1;15+552
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