Expand and simplify (3 + 4*root5)(3 - 2*root5)
Using FOIL to expand the brackets we get
9 - 6root5 + 12root5 + 8*root5^2
Square rooting then squaring a number cancels out, so we are left with 8*5 or 40 for the last term.
Simplify to give
9 + 6*root5 + 40
6*root5 + 49
CM
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