Question

$a ^{2} - b ^{2} = 45$
$a + b = 15$
Atunci
$5a - 5b =$

Answer 1

a² - b² = 45

( a - b ) ( a + b ) = 45

( a - b ) × 15 = 45

a - b = 45 : 15

a - b = 3

5 a - 5 b = 5 ( a - b ) = 5 × 3 = 15

Answer 2

a²-b²=45

a+b=14

(a-b)(a+b)=45⇒15(a-b)=45⇒a-b=45/15⇒a-b=3*|5⇒5a-5b=15.

Bafta!