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\(48-4y^2-4y=-\left(4y^2+4y-48\right)\)
\(=-\left[\left(2y\right)^2+2.2y+1-49\right]\)
\(=-\left[\left(2y+1\right)^2-7^2\right]\)
\(=-\left(2y-6\right)\left(2y+8\right)\)
\(48-4y^2-4y\)
\(=-\left(4y^2+4y-48\right)\)
\(=-\left(4y^2+4y+1-49\right)\)
\(=-\left[\left(2y+1\right)^2-7^2\right]\)
\(=-\left(2y+1-7\right)\left(2y+1+7\right)\)
\(=-\left(2y-6\right)\left(2y+8\right)\)
\(=-4\left(y-3\right)\left(y+4\right)\)
\(A=\left(x^2-4y^2\right)\left(x^2-2xy+4y^2\right)\left(x^2+2xy+4y^2\right)\)
\(A=\left(x-2y\right)\left(x+2y\right)\left(x^2-2xy+4y^2\right)\left(x^2+2xy+4y^2\right)\)
\(A=\left(x-2y\right)\left(x^2+2xy+4y^2\right)\left(x+2y\right)\left(x^2-2xy+4y^2\right)\)
\(A=\left[x^3-\left(2y\right)^3\right]\left[x^3+\left(2y\right)^3\right]\)
\(A=\left[x^3-8y^3\right]\left[x^3+8y^3\right]\)
\(A=x^6-64y^6\)
`9x^2+4y^2-12xy+6x-4y+1`
`=(3x)^2-2.3x.2y+(2y)^2+2(3x-2y)+1`
`=(3x-2y)^2+2(3x-2y)+1`
`=(3x-2y+1)^2`
(1)\(\left(3x\right)^2+2×3x+y^2=\left(3x+y\right)^2\)
(2)\(-x^2+6x-9=-\left(x^2-6x+9\right)=-\left(x^2-6x+3^2\right)=-\left[\left(x-3\right)^2\right]\)
(3)\(x^2+4xy+4y^2=x^2+2×x×2y^2+\left(2y\right)^2=\left(x+2y\right)^2\)
\(A=x^2+2xy+y^2-4x-4y+1\)
\(=\left(x+y\right)^2-4\left(x+y\right)+1\)
\(=3^2-4.3+1\)
\(=-2\)
- (5 + 4y) (5 - 4y) = - [52 - (4y)2] = - (25 - 16y2) = - 25 + 16y2 = 16y2 - 25
-(5+4y)(5-4y) = - ( 52 - 16 y2) = -( 25 - 16y2)