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Problem



Solution:

$(2a^2 + 5b^2)(4a^2 - 7b^2) = 8a^4 + 6a^2b^2 - 35b^4$
$(-4a - \frac{2}{a})^2 = 16a^2 + \frac{4}{a^2} + 16$
$(4x - 3y)^2 - (3x - 4) = 16x^2 - 24xy - 3x + 9y^2 + 4$.