View Full Version : Can you help me solve this math problem
toneisha
Nov 17, 2011, 08:26 AM
math x=7y-42x-3y=14
Curlyben
Nov 17, 2011, 08:34 AM
Seems to have become a little jumbled.
Would you please clarify your question.
jcaron2
Nov 17, 2011, 11:25 AM
math x=7y-42x-3y=14
I think that's supposed to be two different equations, yes?
x=7y-42 and
x-3y=14
If so, the first equation tells you exactly what x is equal to. You can just substitute that expression in place of the x in the second equation. In other words, wherever you see an x in the second equation, write (7y-42) instead.
That will give you an equation with only one variable, y, which you should be able to easily solve for. Then you just have to plug that y value back into the first equation to get the value of x.
If you want to check your answers when you're all done, plug the values you got for x and y into both equations, and make sure they work out to be true. (For the second equation, for example, after you plug in x and y, you should end up with 14 = 14).
Aurora2000
Nov 18, 2011, 08:15 AM
I am a newbie, and I first apologize if mimeTex is not good.
If it reads x=7y-42,\ x-3y=14, then see jcaron2's answer.
If it reads x=7y-4,\ 2x-3y=14, you have 2 (equivalent) choices:
1. Substitute 7y-4 in place of x, thus you have 2(7y-4)-3y=14
2. x=7y-4 is the same as 2x=14y-8, then the difference between these equations gives you 0=11y-22\Longrightarrow\ y=2
In both cases you have a one variable equation. There is no need to check solutions if you do things correctly, and linear equations never gets problems (as sign choices, singularities, etc.).
jcaron2
Nov 18, 2011, 11:22 AM
I bet your interpretation is correct (the one where the gap is between the 4 and the 2x, not the 42 and the x).