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Expand the following:
(y+4)^2

(y+4) (y+4) = (y) (y) + (y) (4) + (4) (y) + (4) (4):
y y+4 y+4 y+4 4

y y = y^2:
y^2+4 y+4 y+4 4

4×4  =  16:
y^2+4 y+4 y+16

4 y+4 y = 8 y:
Answer: |  y^2+8 y+16