Question

rezolvati ecuația x*x=5

Answer 1

x²=5

x²-5=0

x²-(√5)²=0

(x-√5)(x+√5)=0

x1=√5; x2=-√5

S={-√5;√5}

Answer 2

x²= 5

x²- 5=0

x²- (√5)² = 0  

Folosim a² - b² = (a - b)·(a + b)

(x - √5)·(x + √5) = 0

x - √5 = 0 => x = √5

x + √5 = 0 => x = -√5

x = ± √5