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S2−8S+4m−3=0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; color: rgb(40, 40, 40); font-family: helvetica, arial, sans-serif; position: relative; background-color: rgb(247, 247, 247);">Xét hàm số f(x)=x2+1−2x+1+2x" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">f(x)=x2+√1−2x+√1+2xf(x)=x2+1−2x+1+2x f′(x)=2x−11−2x+11+2x" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">f′(x)=2x−1√1−2x+1√1+2xf′(x)=2x−11−2x+11+2x =x(2+41−2x1+2x(1+2x+1−2x))" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">=x(2+4√1−2x√1+2x(√1+2x+√1−2x))=x(2+41−2x1+2x(1+2x+1−2x)) f′(x)=0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">f′(x)=0f′(x)=0 khi và chỉ khi x=0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">x=0x=0 Do đó ta có Bảng biến thiên (tự vẽ) +Nếu x≥0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">x≥0x≥0 thì f′(x)≥0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">f′(x)≥0f′(x)≥0 suy ra .... +Nếu x≤0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">x≤0x≤0 thì f′(x)≤0" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">f′(x)≤0f′(x)≤0 suy ra .... Tóm lại là, từ bảng biến thiên ta được: m≤f(0)=2" role="presentation" style="display: inline-block; line-height: 0; font-size: 14.04px; word-wrap: normal; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; padding-top: 1px; padding-bottom: 1px; position: relative; background-color: rgb(247, 247, 247);">m≤f(0)=2m≤f(0)=2
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