Notice that the first and last terms are separated by a negative, and that they are perfect squares.
4x2 - 25y2
Find the square roots of these terms.
The factored answer is a FOIL multiplication, using these square roots. One factor adds them, the other subtracts them.
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Example:
4x2 - 25y2
Use the square roots of the two parts: 2x and 5y
one factor is + and one is -
= (2x + 5y) (2x - 5y)
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