Question

Daca a patrat - b patrat = 39 , si a - b = 3 . Calculati a + b .

Answer 1

$a^2-b^2=(a-b)(a+b)=3(a+b)=39$
⇒ $a+b= \frac{39}{3}=13$

Answer 2

a²-b² este egal conform formulei cu (a-b)·(a+b)=39
Dar a-b=3 deci a+b=39÷3 = 13