Answer:
1) 5(a^2+b^2) = 125
2) ab = -12
Step-by-step explanation:
a + b = 1
a = 1 - b --(1)
a - b = 7 --(2)
sub (1) into (2):
1 - b - b = 7
-2b = 6
b = -3
when b = -3, a = 4
therefore,
1) 5(a^2+b^2) = 5(4^2 + (-3)^2) = 5(25) = 125
2) ab = 4(-3) = -12
