Question 156564
27 a(cubed) + b(cubed) divided by 3a+b

= [(3a)^3 + b^3] / [3a+b]
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You have "a difference of cubes.
That factors as (3a+b)((3a)^2 -(3a)b+b^2)
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The 3a+b factors in the numerator and in the denominator cancel and you get:
 
= (3a)^2 - (3a)b + b^2

= 9a^2 - 3ab + b^2
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Cheers,
Stan H.