Question

a^2-b^2=45 si a+b=15 atunci 5a-5b este?

Answer 1

$a^2-b^2=45 \Leftrightarrow (a+b)(a-b)=45 \Leftrightarrow 15(a-b)=45. \\ \\ 15(a-b)=45 \Rightarrow 5(a-b)=15 \Leftrightarrow \boxed{5a-5b=15}.$

Answer 2

a² - b² = 45
(a + b) (a - b) = 45
15(a - b) = 45     | : 3
5(a - b) = 15
a - b = 15 : 5
a - b = 3
5(a - b) = 5 * 3 = 15
5a - 5b = 15