~ Bạn tham khảo ~
`a, (x-2)(x+3) + (x+1)^2`
`= x^2 + 3x - 2x - 6 + x^2 + 2x + 1`
`= 2x^2 + 3x - 5`
`b, 2/[x+3] + 3/[x-3] + [4x-30]/[x^2 - 9]`
ĐK : `x\ne+-3`
`= [2(x-3)]/[(x+3)(x-3)] + [3(x+3)]/[(x-3)(x+3)] + [4x-30]/[(x-3)(x+3)]`
`= [2x-6+3x+9 + 4x - 30]/[(x-3)(x+3)]`
`= [9x-27]/[(x-3)(x+3)]`
`= [9(x-3)]/[(x-3)(x+3)]`
`= 9/[x+3]`
