Really need help

[mild shale]

Can someone please tell me what to do for this question? I haven't done math in so long.

[smoky hull]

1. Wait patiently for a helper to come along.
2. Once someone helps you, say thank you and close the thread with:

+close

3. Feel free to nominate the person for helper of the week in #helper-nominations
4. Do not ping the mods, unless someone is breaking the rules.
5. If you're happy with the help you got here, and the server overall, you can contribute financially as well:

[grim portal]

8x1+4x2=-36 is just 4*(2x1+x2=-9), so it's just the points that satisfy 2x1+x2=-9

[mild shale]

I noticed that the second equation is 4 times the first one. but how would i enter the answer?

[grim portal]

well (x1,x2) lies on 2x1+x2=-9, so (x1,x2)=(x1,-2x1-9)

so it's clear the solution set is (0,-9) + x1(1,-2)

[mild shale]

Can I ask how you know where to place the numbers?

I actually do not understand at all

[grim portal]

algebra

$2x_1+x_2=-9\implies x_2=-2x_1-9$

[plain geyser]

Omegabet_

[grim portal]

so it's clear $(x_1,x_2)=(x_1,-2x_1-9)=(x_1,-2x_1)+(0,-9)$

[plain geyser]

Omegabet_

[grim portal]

just algebra in R / R^2

[mild shale]

OK, that I understand. But I didn't know I had to do that.