Đáp án:
Giải thích các bước giải:
a, 2x(x+5)=(x+3)²+(x-1)²+20
⇔2x²+10x=x²+6x+9+x²-2x+1+20
⇔2x²-x²-x²+10x-6x+2x=30
⇔6x=30
⇔x=5
b,(2x-2)²=(x+1)²+3(x-2)(x+5)
⇔4x²-8x+4=x²+2x+1+3(x²+3x-10)
⇔4x²-8x+4=x²+2x+1+3x²+9x-30
⇔4x²-8x-x²-3x²-2x-9x=-33
⇔-19x=-33
⇔x=33/19
c,(x-1)²+(x+3)²=2(x-2)(x+1)+38
⇔x²-2x+1+x²+6x+9=2(x²-x-2)+38
⇔6x=25
⇔x=25/6
d,(x+2)³-(x-2)³=12x(x-2)-8
⇔(x+8)(x²-2x+4)-(x-8)(x²+2x+4)=12x²-24x-8
⇔-12x²+24x+40=0
⇔·x≈3,08
·x≈-1,08