What do you add to #y^2 - 4y# to make it a perfect square?

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Answer 1 · 2017-10-09T07:22:51

see below

a perfect square for a quadratic expression is found from the identity

#(a+-b)^2=a^2+-2ab+b^#

for

#y^2-4y#

to make it a perfect square we add half the coefficient of the y term and square it

#y^2-4y+color(red)(2^2#

this will then give us

#(y-2)^2#