Work Step by Step
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$. The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$. Hence here: $(x+4)^2=x^2+2\cdot4x+4^2=x^2+8x+16$
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