Question
Simplify:$(7a +5b)^2 - (7a - 5b)^2$
✓
Answer
$(7a + 5b)^2 - (7a - 5b)^2$
$= (7a)^2 + (5b)^2 + 2(7a)(5b) - [(7a)^2 + (5b)^2- 2(7a)(5b)]$
$= 49a^2+ 25b^2 + 70ab - [49a^2 + 25b^2 - 70ab]$
$= 70a + 70ab$
$= 140ab.$
$= (7a)^2 + (5b)^2 + 2(7a)(5b) - [(7a)^2 + (5b)^2- 2(7a)(5b)]$
$= 49a^2+ 25b^2 + 70ab - [49a^2 + 25b^2 - 70ab]$
$= 70a + 70ab$
$= 140ab.$
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