a) - 7x2 (3x - 4y) = - 21x3 + 28 x2y
b) (x - 3)(5x - 4) = 5x2 - 4x - 15x + 12 = 5x2 - 19x + 12
c) (2x - 1)2 = (2x)2 - 2.2x.1 + 12 = 4x2 - 4x + 1
d) (x + 3)(x - 3) = x2 - 32
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\(-7x^2\left(3x-4y\right)=-21x^3+28x^2y\)
\(\left(x-3\right)\left(5x-4\right)=5x^2-19x+12\)
\(\left(2x-1\right)^2=4x^2-4x+1\)
\(\left(x+3\right)\left(x-3\right)=x^2-9\)
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