Question

3. If x2 + y2 = 99 and xy = 9, find x-y​

Answer 1

Question:

If $x^2 + y^2 = 99$ and xy = 9, find x-y.

Answer:

By identity $(x-y)^2=x^2+y^2-2xy$,we have:

$\sf (x-y) ^2=99-18 \\\\\sf =(x-y) ^2=81 \\\\\sf = (x-y) =\sqrt{81}= x-y=9$

Hence, x-y=9