Answer
h$^2$
Work Step by Step
(A+B)(A-B)=A$^2$-B$^2$
($\sqrt {h^2+1}$+1)($\sqrt {h^2+1}$-1)
($\sqrt {h^2+1}$)$^2$-(1)$^2$
h$^2$+1-1
h$^2$
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