Đáp án:
`A=3x²+2y²-xy+15`
`B=100x²`
`C=y³+16x²-8x`
Giải thích các bước giải:
`A=2y(x+y)+3x(x-y)+15`
`=2xy+2y²+3x²-3xy+15`
`=3x²+2y²+(2xy-3xy)+15`
`=3x²+2y²-xy+15`
`B=(7x+5)²+(3x-5)²-(10-6x)(5+7x)`
`=(7x+5)²-(10-6x)(5+7x)+(3x-5)²`
`=(7x+5)²+(6x-10)(7x+5)+(3x-5)²`
`=(7x+5)²+2.(7x+5).(3x-5)+(3x-5)²`
`=(7x+5+3x-5)²`
`=(10x)²`
`=100x²`
`C=(2x+y)(y²+4x²-2xy)-8x(x-1)(x-1)`
`=(2x+y)(4x²-2xy+y²)-8x(x-1)²`
`=(2x+y)[(2x)²-2x.y+y²]-8x(x²-2x+1)`
`=(2x)³+y³-8x³+16x²-8x`
`=8x³+y³-8x³+16x²-8x`
`=(8x³-8x³)+y³+16x²-8x`
`=y³+16x²-8x`
