Đáp án:
`15)x=22/5`
Giải thích các bước giải:
`15)(4x+3)³-(4x+1)(16x²-4x+1)=36x(4x+3)-x(x-1)+(x+2)²`
`⇔(4x)³+3.(4x)².3+3.4x.3²+3³-(4x+1)[(4x)³-4x.1+1³]=144x²+108x-x²+x+x²+4x+4`
`⇔64x³+144x²+108x+27-[(4x)³+1³]=144x²+(-x²+x²)+(108x+x+4x)+4`
`⇔64x³+144x²+108x+27-(64x³+1)=144x²+113x+4`
`⇔64x³+144x²+108x+27-64x³-1=144x²+113x+4`
`⇔(64x³-64x³)+144x²+108x+(27-1)=144x²+113x+4`
`⇔144x²+108x+26=144x²+113x+4`
`⇔144x²+108x-144x²-113x=4-26`
`⇔-5x=-22`
`⇔x=22/5`
Vậy `x=22/5`
