Question

B = (x+3)^2 + (x-3) - 2 (x+2) (x-4) tại x= 2/5

Answer 1

(x+3)²+(x-3)-2(x+2)(x-4)

=x²+6x+9+x-3-(2x²-4x-16)

=x²+6x+9+x-3-2x²+4x+16

=-x²+11x+22

Tại x=\(\dfrac{2}{5}\), ta có: \(-\left(\dfrac{2}{5}\right)^2+11.\dfrac{2}{5}+22=26,24\)