Question

Solve the following system.

4x^2 + 9y^2 =72
x^2 - y^2 = 5

The solutions are:
(), (), (), and ()
(remember to include the commas)

Answer 1

@paki

Answer 2

solving for y from eq1

when x = 3

4x^2 + 9y^2 = 72
4(3)^2 + 9y^2 = 72
36 + 9y^2 = 72
9y^2 = 72 - 36
9y^2 = 36
y^2 = 4
y = ± √(4)
y = ± 2

y = 2, -2

Answer 3

@Lolipop_Drum312

That does not look like a solution to me.

You have chosen x=3 and x=-3 but not 'solved' for them

Answer 4

Here is how you do it. Multiply the second equation by 9 to get

4x^2 + 9y^2 = 72
9x^2 - 9y^2 = 45

Add them to get 13x^2 = 117 ----> x^2 = 9 ----> x = +/- 3.
Now substitute in the second original equation to get y

Answer 5

That is correct

Answer 6

ok good