Question

If xy = 16 and x² + y² = 32, then the value of (x + y) is:

• A. ±10
• B. ±4
• C. ±8
• D. ±6

Answer 1

Answer:

C. ±8

Solution:

Given:

x² + y² = 32 and xy = 16

Formula:

(x + y)² = x² + y² + 2xy

Calculation:

(x + y)² = x² + y² + 2xy

⇒ (x + y)² = 32 + 2 $\times$ 16 

⇒ (x + y)² = 32 + 32

⇒ (x + y)² = 64

⇒ (x + y) = ±8