Đáp án+Giải thích các bước giải:
`a) (2x+5)^2-(x-9)^2`
`=(2x+5-x+9)(2x+5+x-9)`
`=(x+14)(3x-4)`
`b) (3x+1)^2-4(x-2)^2`
`=[3x+1-2(x-2)][3x+1+2(x-2)]`
`=(3x+1-2x+4)(3x+1+2x-4)`
`=(x+5)(5x-3)`
`c) 9(2x+3)^2-4(x+1)^2`
`=[3(2x+3)-2(x+1)][3(2x+3)+2(x+1)]`
`=(6x+9-2x-2)(6x+9+2x+2)`
`=(4x-7)(8x+11)`
`d) 4b^2c^2-(b^2+c^2-a^2)^2`
`=(2bc-b^2-c^2+a^2)(2bc+b^2+c^2-a^2)`
`=[a^2-(b^2-2bc+c^2)][(b^2+2bc+c^2)-a^2]`
`=[a^2-(b-c)^2][(b+c)^2-a^2]`
`=(a-b+c)(a+b-c)(b+c-a)(b+c+a)`
`e) (5+x)(5-x)+y(2x-y)`
`=25-x^2+2xy-y^2`
`=25-(x^2-2xy+y^2)`
`=5^2-(x-y)^2`
`=(5-x+y)(5+x-y)`
