Đáp án:
`a)(x-4)/(x+3)`
`b)(2x+3)/(x-2)`
`c)(z-x+y)/(x+y+z)`
Giải thích các bước giải:
`a)(x²-7x+12)/(x²-9)(x\ne+-3)`
`=(x²-3x-4x+12)/(x²-3²)`
`=[x(x-3)-4(x-3)]/[(x+3)(x-3)]`
`=[(x-3)(x-4)]/[(x+3)(x-3)]`
`=(x-4)/(x+3)`
`b)(4x²+12x+9)/(2x²-x-6)(x\ne2,x\ne-3/2)`
`=[(2x)²+2.2x.3+3²]/(2x²-4x+3x-6)`
`=[(2x+3)²]/[2x(x-2)+3(x-2)]`
`=[(2x+3)²]/[(x-2)(2x+3)]`
`=(2x+3)/(x-2)`
`c)(2xy-x²+z²-y²)/(x²+z²-y²+2xz)(x+y+z\ne0,x-y+z\ne0)`
`=[z²-(x²-2xy+y²)]/[(x²+2xz+z²)-y²]`
`=[z²-(x-y)²]/[(x+z)²-y²]`
`=[(x-y+z)(z-x+y)]/[(x+y+z)(x-y+z)]`
`=(z-x+y)/(x+y+z)`
