Question

Rút gọn các biểu thức sau:

a. (x+5)²-4x(2x+3)²-(2x-1)(x+3)(x-3)

b. -2x(3x+2)(3x-2)+5(x+2)²-(x-1)(2x-1)(2x+1)

Answer 1

a: Ta có: \(\left(x+5\right)^2-4x\left(2x+3\right)^2-\left(2x-1\right)\left(x+3\right)\left(x-3\right)\)

\(=x^2+10x+25-4x\left(4x^2+12x+9\right)-\left(2x-1\right)\left(x^2-9\right)\)

\(=x^2+10x+25-16x^3-48x^2-36x-2x^3+18x+x^2-9\)

\(=-18x^3-46x^2-8x+16\)