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19 tháng 1 2020

a) \(12x-9-4x^2\)

\(=-\left(4x^2-12x+9\right)\)

\(=-\left(2x-3\right)^2\)

b)\(1-9x+27x^2-27x^3\)

\(=\left(1-3x\right)^{^3}\)

c)\(\frac{x^2}{4}+2xy+4y^2-25\)

\(=\left(\frac{x}{2}+2y\right)^2-5^2\)

\(=\left(\frac{x}{2}+2y-5\right)\left(\frac{x}{2}+2y+5\right)\)

d)\(\left(x^2-4x\right)^2-8\left(x^2-4x\right)+15\)

\(=\left(x^2-4x\right)^2-3\left(x^2-4x\right)-5\left(x^2-4x\right)+15\)

\(=\left(x^2-4x\right)\left(x^2-4x-3\right)-5\left(x^2-4x-3\right)\)

\(=\left(x^2-4x-5\right)\left(x^2-4x-3\right)\)

\(=\left(x^2+x-5x-5\right)\left(x^2-4x-3\right)\)

\(=\left[x\left(x+1\right)-5\left(x+1\right)\right]\left(x^2-4x-3\right)\)

\(=\left(x-5\right)\left(x+1\right)\left(x^2-4x-3\right)\)

Chúc bạn học tốt !

1 tháng 10 2018

d

\(x^4+2x^3-4x-4\)

\(=\left(x^4+2x^3+x^2\right)-\left(x^2+4x+4\right)\)

\(=\left(x^2+x\right)^2-\left(x+2\right)^2\)

\(=\left(x^2-2\right)\left(x^2+2x+2\right)\)

5 tháng 1 2019

\(\frac{2}{5}x\left(y-1\right)-\frac{2}{5}y\left(y-1\right)\)

\(=\left(y-1\right)\left[\left(\frac{2}{5}x-\frac{2}{5}y\right)\right]\)

\(=\left(y-1\right)\frac{2}{5}\left(x-y\right)\)

5 tháng 1 2019

\(\frac{1}{25}x^2-64y^2\)

\(=\left(\frac{1}{5}x\right)^2-8^2\)

\(=\left(\frac{1}{5}x+8\right)\left(\frac{1}{5}x-8\right)\)

19 tháng 10 2016

\(x\left(x+2\right)\left(x+3\right)\left(x+5\right)+9\)

\(=\left(x^2+5x+6\right)\left(x^2+5x\right)+9\)

Đặt \(t=x^2+5x\)ta được;

\(t\left(t+6\right)+9=t^2+6t+9\)

\(=\left(t+3\right)^2=\left(x^2+5x+3\right)^2\)

b)\(x^2+2xy+y^2+2x+2y-15\)

\(=\left(x+y+1\right)^2-4^2\)

\(=\left(x+y+1+4\right)\left(x+y+1-4\right)\)

\(=\left(x+y-3\right)\left(x+y+5\right)\)

c)\(4x^4y^4+1=\left(2x^2y^2-2xy+1\right)\left(2x^2y^2+2xy+1\right)\)

\(1.\)

\(x^2-2x+1-xy-y=\left(x-1\right)^2-y\left(x-1\right)=\left(x-1\right)\left(x-1-y\right)\)

\(2.\)

\(x^3-4x^2+4x-2x+2=x\left(x^2-4x+4\right)-2\left(x-1\right)=x\left(x-2\right)^2-2\left(x-1\right)\)

\(3.\)

\(10x-25-x^2+4y^2=4y^2-\left(x^2-10x+25\right)=4y^2-\left(x-5\right)^2=\left(2y+x-5\right)\left(2y-x+5\right)\)

\(4.\)

\(4x^2-2x+2xy-y=2x\left(2x-1\right)+y\left(2x-1\right)=\left(2x-1\right)\left(2x+y\right)\)

\(5.\)

\(4x\left(x-3\right)^2-3x^2+9x=4x\left(x-3\right)^2-3x\left(x-3\right)=\left(x-3\right)\left(4x^2-12x-3x\right)\)