If a +b =1 and a-b = 7, find the values of : 1) 5(a^2 +b^2) ii) ab

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

36 girls

step-by-step explanation:

the 48 boys is 4 parts of the ratio

divide 48 by 4 to obtain one part of the ratio

= 12 ← 1 part of the ratio

3 parts = 3 × 12 = 36 ← number of girls