Question

If a + b = 9, ab = 4, find the value of a + b.
If a - b = 5, a + b2 = 49, find the value of ab.​

Answer 1

$\huge\underline\bold\red{AnswEr}$

a+b=9

Squaring both the sides

=>a²+b²+2ab=81

Substituting value of 'ab' in equation

=>a²+b²+2*4=81

=>a²+b²=73

Answer 2

Explanation:

a+b=9 ab=4

(a+b)^2=a^2+b^2+2ab

a^2+b^2=(a+b)^2-2ab

=(9)^2-2(4)

=81-8

=73

(a-b)^2=a^2+b^2-2ab

=(73)-2(4)

=65

a-b=√65

2) a-b=5, a^2+b^2=49

(a-b)^2=a^2+b^2-2ab

(5)^2=(49)-2(ab)

25-49=(-2ab)

12=ab