Question

if a + b =7 and ab =11 then find the value of a-b​

Answer 1

Answer:

given,

ab=11

a+b = 7

square both side

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

7^2 = a^2+b^2+2×11

49 = a^2+b^2+22

a^2+b^2=27

now,

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

(a-b)^2 = 27-22

a-b = √5

now,

a+b=7 ---------eq 1

a-b = √5 ---------eq 2

eq 1 + eq 2

2a = 7+√5

a = 7+√5/2