Question

If a is 4 greater than b and a^2+b^2=10, what is the value of ab?
a)13
b)6
c)3
d)-3
e)-6

Answer 1

a=4+b, now substitute 4+b at the place of a in the equation \[a ^{2}+b ^{2}=10\]

Answer 2

b=x
a=x+4
sub values in the equation
get the answer