Đáp án:
`(x+3)(x+5)(x-5)(x-3)`
Giải thích các bước giải:
`x^4-34x^2+225`
`=x^4-3x^3+3x^3-9x^2-25x^2+75x-75x+225`
`=x^3(x-3)+3x^2(x-3)-25x(x-3)-75(x-3)`
`=(x^3+3x^2-25x-75)(x-3)`
`=(x^3-5x^2+8x^2-40x+15x-75)(x-3)`
`=[x^2(x-5)+8x(x-5)+15(x-5)](x-3)`
`=(x^2+8x+15)(x-5)(x-3)`
`=(x^2+3x+5x+15)(x-5)(x-3)`
`=[x(x+3)+5(x+3)](x-5)(x-3)`
`=(x+3)(x+5)(x-5)(x-3)`