Question

If x ^2 + y ^2= 9 and xy = 8, then x + y is equal to​

Answer 1

Answer:

5.

Step-by-step explanation:

given,

x²+y²=9

and

xy=8

let us use the formula

(x+y)²= x²+y²+2xy

that implies,

(x+y)²= 9+(2×8)

=> x+y= √(9+16)

=> x+y= √25

=> x+y= 5.

Answer 2

Your Solution:

Identity used a² + b² + 2ab = (a + b)² can be written as a² + b² = (a + b)² - 2ab. Just 2ab in L.H.S is taken to R.H.S which is -2ab.

x² + y² = 9

» (x + y)² - 2xy = 9

» (x + y)² - 2(8) = 9

» (x + y)² - 16 = 9

» (x + y)² = 25

» x + y = √25

» x + y = 5

I hope you got it.

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