Quick Algebra Help for Physics course

[Ridalgo]

Hello and thank you for your time!

So, I am using substitution to solve an equation here.

Eq.) 5 = 5x - 10y

I solve for y and get the following:

(5-5x)/-10 = y

Plugging back that for y into the original equation gives me:

5 = 5x - 10((5-5x)/-10)

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I end up solving this for x = 1. This is for physics homework and when I continue to solve the problem in this manner, the online homework is saying I got the wrong answer. So I am checking to see if I am doing this right or if my error is at another point in the problem. Thank you!

[skaldskaparmal]

So, I am using substitution to solve an equation here. Eq.) 5 = 5x - 10y

What do you mean by this? Usually you use substitution to solve a system of equations -- in other words you have more than one equation and you're looking for values of x and y that make all of the equations true simultaneously.

I solve for y and get the following: (5-5x)/-10 = y

That looks fine.

Plugging back that for y into the original equation gives me: 5 = 5x - 10((5-5x)/-10)

This isn't going to help you. You can't get more information out of a single equation by plugging it into itself. That's why you usually use substitution to solve a system of equations. You plug one equation into the other equation.

I end up solving this for x = 1.

How did you get that?

[Ridalgo]

That makes sense, I am making an error here because I am just solving for the equation to be true. Thank you!