Question

Rút gọn: 
a) A=(4-5x)²-(3+5x)²
b) B=(3x-1)(1+3x)-(3x+1)²
c) C=(2x+5)³-(2x-5)³-(120x²+49)
d) D=(2a-b+2)³-6(2a-b+2)²+12(2a-b+2)-8-(2a-b)³

Answer 1

a) A=(4-5x)²-(3+5x)²=(4-5x-3-5x)(4-5x+3+5x)=(-25x+1)1=-25x+1

Answer 2

B=(3x-1)(1+3x)-(3x+1)²=9x²-1-(3x+1)²=9x²-1-(9x²+6x+1)=9x²-1-9x²-6x-1=-6x-2=-2(3x+1)