Question

rút gọn bt:

5(x – 2)(x + 2) - 1/2(6 – 8x)^2 + 17

 

Answer 1

   5(x - 2)(x + 2) - 1/2(6-8x)² + 17
= 5(x² - 4) - 1/2(36 - 96x + 64x²) + 17
= 5x² - 20 - 18 + 48x - 32x² + 17
= -27x² + 48x - 21

Answer 2

\(5\left(x-2\right)\left(x+2\right)-\frac{1}{2}\left(6-8x\right)^2+17\)

= \(5\left(x^2-4\right)-\frac{1}{2}\left[2\left(3-4x\right)\right]^2+17\)

= \(5x^2-20-2\left(3-4x\right)^2+17\)

= \(5x^2-3-2\left(3-4x\right)^2\)

= \(5x^2-3-2\left(9-24x+16x^2\right)\)

= \(5x^2-3-18+48x-32x^2\)

= \(-27x^2+48x-21\)

= \(-3\left(9x^2-16x+7\right)\)