Question

Answer 1

Lời giải:

a. 

$A=(x^2+6x+9)+(x^2-9)-2(x^2-2x-8)$

$=x^2+6x+9+x^2-9-2x^2+4x+16=10x+16=10.\frac{-1}{2}+16=-5+16=11$

b.

$B=9x^2+24x+16-(x^2-16)-10x=9x^2+24x+16-x^2+16-10x$

$=8x^2+14x+32=8(\frac{-1}{10})^2+14.\frac{-1}{10}+32=\frac{767}{25}$

Answer 2

c.

$C=(x+1)^2-(2x-1)^2+3(x-2)(x+2)$

$=(x+1-2x+1)(x+1+2x-1)+3(x^2-4)$

$=(2-x).3x+(3x^2-12)=6x-3x^2+3x^2-12=6x-12=6.1-12=-6$

d.

$D=(x-3)(x+3)+(x-2)^2-2x(x-4)$

$=(x^2-9)+(x^2-4x+4)-(2x^2-8x)$

$=x^2-9+x^2-4x+4-2x^2+8x$

$=(x^2+x^2-2x^2)+(-4x+8x)+(-9+4)$

$=4x-5=4(-1)-5=-9$