The problem
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Step 3 going to step 4, where did the x^2 from (x^2+2xh+h^2) go? Also where is the -3x^2?
Answer provided by our tutors
We pull the Greatest Common Factor for 3(x^2+2xh+h^2) and - 3x^2 in front the brackets (that is 3).
What is left in the brackets is x^2 + 2xh + h^2 - x^2.
Next we simplify x^2 + 2xh + h^2 - x^2 and get 2hx + h^2.
Now we can write:
3(x^2+2xh+h^2) - 3x^2 = 3(x^2 + 2xh + h^2 - x^2) = 3(2hx + h^2)
That is how from 3(x^2+2xh+h^2) - 3x^2 we get 3(2hx + h^2).