Question

Hello I am mother trying to explain to my 13 year-old daughter the result of this equation:

7x^2+7y-4x^2-4y equals to 3x^2-3y

I just want to know that I am right since my daughter insists that that was not what the teacher had on the board she got 34y which I told her it is no way you get 34y.

Thank you.

Answer 1

7x^2+7y-4x^2-4y equals to 3x^2-3y

7x^2+7y-4x^2-4y = 3x^2-3y
7x^2 - 4x^2 - 3x^2 = -3y + 4y - 7y
0 = -6y
6y = 0
y = 0

sub back in
7x^2 + 0 - 4x^2 = 3x^2 - 0
0 = 0

<b>x can be any number, y = 0</b>

eg. let x = 3, y = 0
LS = 63 + 0 - 36 - 0 = 27
RS = 27 - 0 = 27 , works!

let x = 3, y = 1
LS = 63 + 7 - 36 - 4 = 30
RS = 27 - 3 = 24 , NO GOOD