Question

If \(x+y=5\) and \(x-y=3\), then \(x^2-y^2=\)
9
15
16
25
34

Answer 1

Note that \[(a-b)(a+b)=a^2-b^2\]

Answer 2

Yes.

Answer 3

ok, so
what's \(x+y\) ?

Answer 4

I'm not sure..

Answer 5

it's given in the problem

Answer 6

Oh, 5.

Answer 7

right
what is \(x-y\) ?

Answer 8

3

Answer 9

good
now, given that \((x-y)(x+y)=x^2-y^2\), what is \(x^2-y^2\) ?

Answer 10

So, \(5 * 3\) = \(5^2-3^2\)=25-9=16

Answer 11

no, on the left side you substituted correctly, then you decided to make x=5 and y=3 for some reason

Answer 12

So just, \(5*3\)

Answer 13

yep