Question

3x+3y=10
-9x-9y=-30

Answer 1

Multiply the first equation by -3 and compare it to the second equation. What can you conclude?

Answer 2

do i plug -3 into x or y?

Answer 3

@ranga

Answer 4

Not plug -3. But multiply each term of the first equation by -3.

Answer 5

i got -9x-9y=-30 the second equation

Answer 6

Yes. When you multiply the first equation throughout by -3 you end up with an equation that is exactly the second equation. That means the first and the second are one and the same equation.

We have 2 unknowns x and y. We will need two independent equations to solve and find a unique solution for x and y. But what we have here is two equations which are the same but 2 unknowns. That means this problem does bot have a unique solution.

It has infinite number of solutions.

Answer 7

You can pick any value for x, say x = 0, put it in the first equation and solve for y. You will find the x and y values will automatically satisfy the second equation.
You can pick x = 1, solve for y. x = 2, solve for y and each time both equations will be satisfied. So there is no one solution but infinite number of them. The reason is the two equations are dependent equations.

Answer 8

Thank you so much! that help a lot!