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\(2\left(x-2\right)\left(x+3\right)-x^2+4=0\)
\(2\left(x^2+3x-2x-6\right)-x^2+4=0\)
\(2x^2+6x-4x-12-x^2+4=0\)
\(x^2+2x-8=0\)
\(x^2+4x-2x-8=0\)
\(x\left(x+4\right)-2\left(x+4\right)=0\)
\(\left(x+4\right)\left(x-2\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x+4=0\rightarrow x=\left(-4\right)\\x-2=0\rightarrow x=2\end{cases}}\)
3/
a/ \(2\left(x+1\right)^2-3\left(x-1\right)^2+\left(x+2\right)\left(5-x\right)\)
\(=2\left(x^2+2x+1\right)-3\left(x^2-2x+1\right)+\left(5x-x^2+10-2x\right)\)
\(=2x^2+4x+2-3x^2+6x-3+5x-x^2+10-2x\)
\(=-2x^2+13x+9\)
b/ \(\left(3x-1\right)^3+\left(3x-1\right)^3-6x^2+9\)
\(=2\left(3x-1\right)^3-6x^2+9\)
\(=2\left(\left(3x\right)^3-3\left(3x\right)^2\cdot1+3\cdot3x\cdot1-1\right)-6x^2+9\)
\(=2\left(27x^3-27x^2+9x-1\right)-6x^2+9\)
\(=54x^3-54x^2+18x-2-6x^2+9\)
\(=54x^3-60x^2+18x+7\)
Số hơi dài, nên dễ tính sai -,- tính mik hay cẩu thả có j sai ibbb ạ
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\(\left(x^2-2\right)\left(1-x\right)+\left(x+3\right)\left(x^2-3x+9\right)\)
\(=\left(x^2-x^3-2+2x\right)+\left(x^3+3^3\right)\)
\(=x^2-x^3-2+2x+x^3+27\)
\(=\left(-x^3+x^3\right)+x^2+2x+\left(-2+27\right)\)
\(=x^2+2x+25\)
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Công thức tổng quát:
\(\frac{1}{n\left(n+1\right)}=\frac{1}{n}-\frac{1}{n+1}\)
Do đó:
\(A=\frac{1}{x}-\frac{1}{x+1}+\frac{1}{x+1}-\frac{1}{x+2}+\frac{1}{x+2}-\frac{1}{x+3}+\frac{1}{x+3}-\frac{1}{x-4}+\frac{1}{\left(x-1\right)\left(x+10\right)}\)
Bạn tự làm tiếp nhé.
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a: \(\left(3x+2\right)^2+4x-3x^2+2\left(5x-2\right)\left(5x+2\right)-75x^2\)
\(=9x^2+12x+4+4x-3x^2+50x^2-8-75x^2\)
\(=-19x^2+16x-4\)
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Ta có 2x(2x + 1)2 - 3x(x + 3)(x - 3) - 4x(x + 1)2
= 2x(4x2 + 4x + 1) - 3x(x2 - 9) - 4x(x2 + 2x + 1)
= 8x3 + 8x2 + 2x - 3x3 + 27x - 4x3 - 8x2 - 4x
= 8x3 - 3x3 - 4x3 + 8x2 - 8x2 + 2x + 27x - 4x
= x3 + 25x
a oi hinh nhu sai r con +16x2 nua co a , anh tinh lai ho e duoc kh
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