How do you multiply (sqrtt-y) (sqrtt+y) ?

1 Answer
Alan P.
Sep 13, 2015

(sqrt(t)-y)(sqrt(t)+y)= t-y^2

Explanation:

In general we have a standard formula called the difference of squares:
color(white)("XX")(a^2-b^2) = (a-b)(a+b)

This can be written in reverse as
color(white)("XX")(a-b)(a+b) = a^2-b^2

Substituting
color(white)("XX")sqrt(t) " for "a
and
color(white)("XX")y " for " b

we have
color(white)("XX")(sqrt(t)-y)(sqrt(t)+y)

color(white)("XXX")= (sqrt(t))^2-y^2

color(white)("XXX")=t-y^2

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