Đáp án:
`a)x=-7`
`b)x=1`
Giải thích các bước giải:
`a)(2x²-5)(2x²+5)-4x(x³+1)=3`
`⇔(2x^2)^2-5^2-4x^4-4x=3`
`⇔4x^4-25-4x^4-4x=3`
`⇔(4x^4-4x^4)-4x-25=3`
`⇔-4x-25=3`
`⇔-4x=3+25`
`⇔-4x=28`
`⇔x=28:(-4)`
`⇔x=-7`
Vậy `x=-7`
`b)(12x-5)(4x-1)+(3x-7)(1-16x)=81`
`⇔48x²-12x-20x+5+3x-48x²-7+112x=81`
`⇔(48x²-48x²)+(-12x-20x+3x+112x)+(5-7)=81`
`⇔83x-2=81`
`⇔83x=81+2`
`⇔83x=83`
`⇔x=83:83`
`⇔x=1`
Vậy `x=1`
