Question

If xy = -18 and x2+ y2= 85, then find the value of (x + y).

A) 8 B) 10 C) 9 D) 7

Answer 1

Step-by-step explanation:

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

now putting the values given questions

(x+y)^2= 85 + 2 *(-18)

(x+y)^2=85-36

(x+y)^2=49

x+y=

$\sqrt{49}$

7

Answer 2

Answer:

D) 7

Step-by-step explanation:

WKT

( a + b )² = a² + b² + 2ab

Given

xy = -18

x² + y² = 85

Now

( x + y )² = x² + y² + 2xy

( x + y )² = 85 - 2(18)

( x + y )² = 49

x + y = I 7 I

If IxI > IyI and x > 0

x + y =7

Else If  IxI < IyI and x > 0

x + y = -7

Hope it Helps