Đáp án:
`5)1/(x+2)`
`6)-1/(x^2-4)`
Giải thích các bước giải:
`5)4/(x+2)+3/(2-x)+12/(x²-4)(x\ne+-2)`
`=4/(x+2)-3/(x-2)+12/[(x+2)(x-2)]`
`=[4(x-2)]/[(x+2)(x-2)]-[3(x+2)]/[(x+2)(x-2)]+12/[(x+2)(x-2)]`
`=[4(x-2)-3(x+2)+12]/[(x+2)(x-2)]`
`=(4x-8-3x-6+12)/[(x+2)(x-2)]`
`=(x-2)/[(x+2)(x-2)]`
`=1/(x+2)`
`6)3/(x²-4)+1/(2-x)+1/(x+2)(x\ne+-2)`
`=3/[(x+2)(x-2)]-1/(x-2)+1/(x+2)`
`=3/[(x+2)(x-2)]-(x+2)/[(x+2)(x-2)]+(x-2)/[(x+2)(x-2)]`
`=[3-(x+2)+x-2]/[(x+2)(x-2)]`
`=(3-x-2+x-2)/[(x+2)(x-2)]`
`=-1/[(x+2)(x-2)]`
`=-1/(x^2-4)`
