Question

Se stie ca x+y=4 iar xy=3.Calculati x la patrat +y la patrat. Multumesc!

Answer 1

$x+y=4 \ \ \ |^2 \\\\ (x+y)^2=4^2 \\\\ x^2+2xy+y^2=16 \\\\ x^2+2*3+y^2=16 \\\\ x^2+y^2=16-2*3 \\\\ x^2+y^2=16-6 \\\\ \boxed{x^2+y^2=10}$

Answer 2

x + y = 4
xy = 3
x²+ y² = ?
( x + y)² = x² + 2xy + y²
x² + y² + 2xy = ( x + y)²
x² + y² = ( x + y)² - 2xy, inlocuiesti x + y si xy
x² + y² = 4² - 2 · 3
x² + y² = 16 - 6
x² + y² = 10