(7x-4)^2-(2x+1)^2 9(x+1)^2-1 9(x+5)^2-(x-7)^2 49(y-4)^2-9(y+2)^2

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1. Bđt thứ `3:`

   `a^2-b^2=(a+b)(a-b)`

   `a,` `(7x-4)^2-(2x+1)^2`

   `=[(7x-4)+(2x+1)][(7x-4)-(2x+1)]`

   `=(9x-3)(5x-5)`

   `=3(3x-1).5(x-1)`

   `=15(3x-1)(x-1)`

   `b, 9(x+1)^2-1`

   `=[3(x+1)]^2-1^2`

   `=[3(x+1)+1][3(x+1)-1]`

   `=(3x+4)(3x+2)`

   `c,` `9(x+5)^2-(x-7)^2`

   `=[3(x+5)]^2-(x-7)^2`

   `=[3(x+5)+(x-7)][3(x+5)-(x-7)]`

   `=(3x+15+x-7)(3x+15-x+7)`

   `=(4x+8)(2x+22)`

   `=4(x+2).2(x+22)`

   `=6(x+2)(x+22)`

   `d,` `49(y-4)^2-9(y+2)^2`

   `=[7(y-4)]^2-[3(y+2)]^2`

   `=[7(y-4)+3(y+2)][7(y-4)-3(y+2)]`

   `=(7y-28+3y+6)(7y-28-3y-6)`

   `=(10y-22)(4y-34)`

   `=2(5y-11).2(2y-17)`

   `=4(5y-11)(2y-17)`

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2. Đáp án:

    

   Giải thích các bước giải:

   A=(7x-4)²-(2x+1)²

   A=49x²-56x+16-4x²-4x-1

   A=45x²-60x+15

   A=45x²-45x-15x+15

   A=45x(x-1)-15(x-1)

   A=(x-1)(45x-15)

   B=9(x+1)²-1

   B=9x²+18x+9-1

   B=9x²+18x+8

   B=9x²+6x+12x+8

   B=3x(3x+2)+4(3x+2)

   B=(3x+2)(3x+4)

   C=9(x+5)²-(x-7)²

   C=9x²+90x+225-x²+14x-49

   C=8x²+104x+176

   C=8x²+16x+88x+176

   C=8x(x+2)+88(x+2)

   C=(x+2)(8x+88)

   D=49(y-4)²-9(y+2)²

   D=49y²-196y+196-9y²-36x-36

   D=40y²-232y+160

   D=40y²-200y-32y+160

   D=40y(y-5)-32(y-5)

   D=(y-5)(40y-32)

   Xin 5 sao và ctlhh nhé . Chúc bn học tốt

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