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Answer:
4f^2 -4f +1
Step-by-step explanation:
It can be useful to memorize the form of the square of a binomial:
(a +b)^2 = a^2 +2ab +b^2
Here, you have a=2f and b=-1. Then the square is ...
(2f)^2 +2(2f)(-1) +(-1)^2 = 4f^2 -4f +1
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More generally, the distributive property applies.
(2f -1)^2 = (2f -1)(2f -1) = 2f(2f -1) -1(2f -1)
= (2f)(2f) +(2f)(-1) +(-1)(2f) +(-1)(-1) = 4f^2 -2f -2f +1 = 4f^2 -4f +1