Question

Tính

(x+5)² - 4x(2x+3)² - (2x-1) ( x+3)(x-3)

Answer 1

(x+5)^2-4x(2x+3)^2-(2x-1)(x+3)(x-3)

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

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

=-18x^3-46x^2-8x+34

Answer 2

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

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

\(=\left(x^2+10x+25\right)-4x\left(4x^2+12x+9\right)-\left[2x\left(x^2-9\right)-1\left(x^2-9\right)\right]\)\(=\left(x^2+10x+25\right)-4x\left(4x^2+12x+9\right)-\left(2x^3-18x-x^2+9\right)\)

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

\(=\left(x^2-48x^2+x^2\right)+\left(10x+18x-36x\right)-\left(16x^3+2x^3\right)+\left(25-9\right)\)\(=-46x^2-8x-18x^3+16\)