Question

that follow. 4x – 9y = 7 –2x + 3y = 4 What number would you multiply the second equation by in order to eliminate the x-terms when adding to the first equation? What number would you multiply the second equation by in order to eliminate the y-terms when adding to the first equation?

Answer 1

Explanation:

4x – 9y = 7

–2x + 3y = 4 (2)

You want to eliminate the x-terms when adding to the first equation, so you have to multiple both sides of the equation (2) by 2 like:

4x – 9y = 7

–4x + 6y = 8

-----------------------------(add)

0 - 3y = 15

or y = -5, and x = - 19/2

But if you want to eliminate the y-terms when adding to the first equation, so you have to multiple both sides of the equation (2) by 3, like

4x – 9y = 7

-6x + 9y = 12

-----------------(add)

-2x + 0 = 19

or x = - 19/2 and y = - 5