Question

if a+b=7 and ab=10 find a-b​

Answer 1

Given, (a+b)=7, ab=10

Squaring both sides

⇒(a+b)²=7²

⇒a²+b²+2ab=49

⇒a²+b²=49−2(10)

⇒a² +b² =29

Now,

(a−b)²=a²+b²−2ab

=29−2(10)

=29−20

=9

$\alpha - \beta = \sqrt{9}$

=±3

Answer 2

Given, (a+b)=7, ab=10

We have to Square both sides

=> (a+b)² = 7²

=> a² + b² + 2ab = 49

=> a² + b² + 2(10) = 49 (it is given as => a² + b² = 49 - 2(10) ab = 10)

=> a² + b² = 49 - 2(10)

=> a² + b² = 49 - 20

=>a² + b² = 29

Now a-b =

=> (a-b)² = a²+ b² - 2ab

=> (a-b)² = 29 - 2ab

=> (a-b)² = 29 - 20

=> (a-b)² = 9

=> a-b = √9

=> a-b = 3/-3

[ because -3 × -3 = 9 and 3 × 3 = 9 ]