Question

(ii) If x + y = 9 and xy = 20 , then the value of x^2 - xy +y^2 is​

Answer 1

Answer:

41

Step-by-step explanation:

Given : x+y=9 and xy=20

To Find: the value of x²+y²

Solution:

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

We are given that x+y=9 and xy=20

Substitute the values .

(9)^2=x^2+y^2+2(20)

81=x^2+y^2+40

81-40=x^2+y^2

41=x^2+y^2

Hence the value of x²+y² is 41

Answer 2

ANSWER :–

▪︎ x² - xy + y² = 21

EXPLANATION :–

GIVEN :–

• x + y = 9

• xy = 20

TO FIND :–

• x² - xy + y² = ?

SOLUTION :–

= x² - xy + y²

• We should write this as –

= x² - xy + y² + 2xy - 2xy

= x² + 2xy + y² - 3xy

• We know that –

⇒ (a + b)² = a² + b² + 2ab

• So that –

= (x + y)² - 3xy

• Now put the values –

= (9)² - 3(20)

= 81 - 60

= 21

• Hence , x² - xy + y² = 21 .