Question

The value of (x 2 + y 2), if xy = 15
and x + y = 10 *​

Answer 1

Answer

x² + y² = 70

Given

x + y = 10

xy = 15

To Find

x² + y²

Solution

x + y = 10

On squaring on both sides , we get ,

⇒ ( x + y )² = (10)²

⇒ x² + y² + 2xy = 100

⇒ x² + y² + 2( 15 ) = 100  [ ∵ xy = 15 ]

⇒ x² + y² + 30 = 100

⇒ x² + y² = 100 - 30

⇒ x² + y² = 70

So , x² + y² = 70

Answer 2

Answer:

(x+y)^2=x^2+y^2+2xy

10^2=x^2+y^2+2(15)

100=x^2+y^2+30

x^2+y^2=100-30

x^2+y^2=70