Đáp án + Giải thích các bước giải:
`g) (7x-1)^2-(x+5)^2`
`=[7x-1-(x+5)][7x-1+(x+5)]`
`= (7x-1-x-5)(7x-1+x+5)`
`= (6x-6)(8x+4)`
`= 4.6(x-1)(2x+1)`
`= 24(x-1)(2x+1)`
`h) 4(2x-1)^2-(x-3)^2`
`= [2(2x-1)]^2-(x-3)^2`
`=[2(2x-1)-(x-3)][2(2x-1)+(x-3)]`
`= (4x-2-x+3)(4x-2+x-3)`
`= (3x-1)(5x-5)`
`= 5(3x-1)(x-1)`
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Áp dụng:
HĐT: `A^2-B^2= (A-B)(A+B)`
