Question

Rút gọn biểu thức:

A=\(\text{4(x-1)(x+1)-5x(x-2)+x^2}\)

B=\(\left(y^2+2\right)\left(y-4\right)-\left(2y^2+1\right)\left(\dfrac{1}{2}y-2\right)\)

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

Answer 1

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

\(=4x^2-4-5x^2+10x+x^2\)

\(=10x-4\)

\(M=\left(y^2+2\right)\left(y-4\right)-\left(2y^2+1\right)\left(\dfrac{1}{2}y-2\right)\)

\(=\left(y^2+2\right)\left(y-4\right)-\dfrac{1}{2}\left(2y^2+1\right)\left(y-4\right)\)

\(=\left(y-4\right)\left(y^2+2-y^2-\dfrac{1}{2}\right)\)

\(=\dfrac{3}{2}y-6\)

c)

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

= 3x - 6 - 2x² + 4x - 4x² + 12x + 4x - 12 - x² + 4

= - 7x² + 23x - 14