Question

What is the value of the expression
x² + 2x - 2xy – 2y + y^2 when x - y = 50 ?

Answer 1

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

… = (x - y)² + 2 (x - y)

… = 50² + 2 × 50

… = 2600