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\(\left(2x+3-x+7\right)\left(2x+3+x-7\right)=\left(x+10\right)\left(3x-4\right)\)
\(4\left(x^2-2xy+y^2\right)-\left(9x^2+6xy+y^2\right)=4x^2-8xy+y^2-9x^2-6xy-y^2=-5x^2+2xy=-x\left(5x-2y\right)\)
e)\(\left(2x+3\right)^2-\left(x-7\right)^2=\left(2x+3-x+7\right)\left(2x+3+x-7\right)=\left(x+10\right)\left(3x-4\right)\)
e. (2x + 3)2 - (x - 7)2
= (2x + 3 + x - 7)(2x + 3 - x + 7)
= (3x - 4)(x + 10)
f. 4(x - y)2 - (3x + y)2
= \(\left[2\left(x-y\right)\right]^2-\left(3x+y\right)^2\)
= (2x - 2y)2 - (3x + y)2
= (2x - 2y + 3x + y)(2x - 2y - 3x - y)
= (5x - y)(5x - 3y)
