Đáp án:
`c)x=14`
`d)x=-255/2`
Giải thích các bước giải:
`c)(x-1)³-(x²-3x+9)(x+3)+3(x-2)(x+2)=2`
`⇔x³-3x²+3x-1-(x³+27)+3(x²-4)=2`
`⇔x³-3x²+3x-1-x³-27+3x²-12=2`
`⇔(x³-x³)+(-3x²+3x²)+3x-(1+27+12)=2`
`⇔3x-40=2`
`⇔3x=2+40`
`⇔3x=42`
`⇔x=42:3`
`⇔x=14`
Vậy `x=14`
`d)(2x-1)²+(x+3)²-5(x-7)(x+7)=0`
`⇔4x²-4x+1+x²+6x+9-5(x²-49)=0`
`⇔4x²-4x+1+x²+6x+9-5x²+245=0`
`⇔(4x²+x²-5x²)+(-4x+6x)+(1+9+245)=0`
`⇔2x+255=0`
`⇔2x=-255`
`⇔x=-255/2`
Vậy `x=-255/2`