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đặt câu hỏi
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Tinh tong
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Voi $n$la so nguyen duong. Tinh tong $T=1C^0_n+2C^1_n+3C^2_n+...+(n+1)C^n_n$
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đặt câu hỏi
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pt luong giac
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Giai pt: $2cosx+\frac{1}{3}cos^2(x+\pi)=\frac{8}{3}+sin2x+3cos(x+\frac{\pi}{2})+\frac{1}{3}sin^2x$ |
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sửa đổi
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HELP ME
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Ptdt $AB$:$x+2y-5=0$Ta co:$\frac{-1}{-2}=\frac{2}{4}\Rightarrow \Delta _1//\Delta _2$Goi $M=AB\cap \Delta _1$ Toa do cua M la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -x+2y-7=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=-1\\ y=3 \end{array} \right.$$\Rightarrow M(-1;3)$Goi $N=AB\cap \Delta _2$ toa do cua $N$la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -2x+4y-5=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=5/4\\ y=15/8 \end{array} \right.$$\Rightarrow N(5/4;15/8)$$C $ cach deu $\Delta_1 ,\Delta _2 \Rightarrow C$ la trung diem cua $MN:\left\{ \begin{array}{l} x_C=\frac{-1+5/4}{2}\\ y_C=\frac{3+15/4}{2} \end{array} \right.$Vay$ C(\frac{1}{8};\frac{27}{8})$
Ptdt $AB$:$x+2y-5=0$Ta co:$\frac{-1}{-2}=\frac{2}{4}\Rightarrow \Delta _1//\Delta _2$Goi $M=AB\cap \Delta _1$ Toa do cua M la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -x+2y-7=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=-1\\ y=3 \end{array} \right.$$\Rightarrow M(-1;3)$Goi $N=AB\cap \Delta _2$ toa do cua $N$la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -2x+4y-5=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=5/4\\ y=15/8 \end{array} \right.$$\Rightarrow N(5/4;15/8)$$C $ cach deu $\Delta_1 ,\Delta _2 \Rightarrow C$ la trung diem cua $MN:\left\{ \begin{array}{l} x_C=\frac{-1+5/4}{2}\\ y_C=\frac{3+15/8}{2} \end{array} \right.$Vay$ C(\frac{1}{8};\frac{39}{16})$
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giải đáp
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HELP ME
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Ptdt $AB$:$x+2y-5=0$ Ta co:$\frac{-1}{-2}=\frac{2}{4}\Rightarrow \Delta _1//\Delta _2$ Goi $M=AB\cap \Delta _1$ Toa do cua M la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -x+2y-7=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=-1\\ y=3 \end{array} \right.$ $\Rightarrow M(-1;3)$ Goi $N=AB\cap \Delta _2$ toa do cua $N$la nghiem cua he:$\left\{ \begin{array}{l} x+2y-5=0\\ -2x+4y-5=0 \end{array} \right.\Leftrightarrow \left\{ \begin{array}{l} x=5/4\\ y=15/8 \end{array} \right.$ $\Rightarrow N(5/4;15/8)$ $C $ cach deu $\Delta_1 ,\Delta _2 \Rightarrow C$ la trung diem cua $MN:\left\{ \begin{array}{l} x_C=\frac{-1+5/4}{2}\\ y_C=\frac{3+15/8}{2} \end{array} \right.$ Vay$ C(\frac{1}{8};\frac{39}{16})$ |
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bình luận
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giup gio
cach giai rat hay a, e cam on!
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giải đáp
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giup minh bai pt nay voi
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$PT\Leftrightarrow x^4-2x^2+1-(x^2+4x+4)=0$ $\Leftrightarrow (x^2-1)^2-(x+2)^2=0$
$\Leftrightarrow (x^2+x+1)(x^2-x-3)=0$
$\Leftrightarrow x^2-x-3=0$ ban tu tim nghiem nhe |
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giải đáp
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này gió à
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cau a nek: +)Chon tuy u so co 3 chu so khac nhau co:$A^3_8-A^2_7=294 $ so. +)Chon so co 3 chu so ma tong cac chu so lon hon $15:$ goi so can tim co dang:$\overline{abc}\Rightarrow (a;b;c)={(3;6;7);(4;6;7);(5;6;7)}$ $\Rightarrow $ co $3.A^3_3=18$ so co dang $\overline{abc} $ ma $(a+b+c>15)$ Vay co :$294-18=276$ so tm dkbt
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đặt câu hỏi
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giup gio
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Có bao nhiêu số nguyên dương không lớn hơn $1000$ mà chia hết cho $4$ hoặc cho $7$?
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đặt câu hỏi
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Gioi han cua day so
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1,Tim: $lim(\frac{1}{2}+\frac{3}{2^2}+\frac{5}{2^3}+..+\frac{2n-1}{2^n})$ 2,Cho $(x_k):x_k=\frac{1}{2!}+\frac{2}{3!}+\frac{3}{4!}+...+\frac{k}{(k+1)!}$ Tinh: $lim\sqrt[n]{x^n_1+x^n_2+...+x^n_{2014}}$ |
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