Please show every step
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You need to apply a method known as Differences of Squares. Differences of Squares tells us that if you have an algebraic expression in form a^2 - b^2, you can write it as (a-b)*(a+b), for instance 4^2 - 2^2 = (4-2)*(4+2) = 12
36 = 6^2
so we have 6^2 - (x+3y)^2, we apply the method.
We now have (6-(x+3y))*(6+(x+3y)) = (6-x-3y)*(6+x+3y).
36 = 6^2
so we have 6^2 - (x+3y)^2, we apply the method.
We now have (6-(x+3y))*(6+(x+3y)) = (6-x-3y)*(6+x+3y).
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36 - (x+3y)^2
36 - (x+3y)(x+3y) (Use FOIL--First, Outer, Inner, Last)
36 - x^2 + 6xy + 9y^2
36 - (x+3y)(x+3y) (Use FOIL--First, Outer, Inner, Last)
36 - x^2 + 6xy + 9y^2
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36 - (x + 3y)² = 6² - (x + 3y)²
this is the difference of the squares identity
6² - (x + 3y)² = [6 - (x + 3y)][6 + (x + 3y)]
==> (6 - x - 3y)(6 + x + 3y)
this is the difference of the squares identity
6² - (x + 3y)² = [6 - (x + 3y)][6 + (x + 3y)]
==> (6 - x - 3y)(6 + x + 3y)
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-(x+3 y-6) (x+3 y+6)