Question

if x+y=5 and x-y=3 find xy

Answer 1

x+y=5____(1)
x-y=3___(2)
equating (1)and (2)
2x=8
x=8/2
x=4
putting the value of x=4 in equation 1/equation 2
equation (1)
x+y=5
4+y=5
y=5-4
y=1
then,
xy=4×1
xy=4

Answer 2

by formula-
(a-b)^2=(a+b)^2-4xy
3^2=5^2-4xy
25-9=4xy
by solving,
xy=4