Solve using substitution: -3x + y = 1 and 4x + y = 8. Put your answer in coordinate form.

Question

jtug6 · Answer

Solve for one variable of either equation. How about the first? what does y equal for the first equation?

saadi101 · Answer

I'm not sure how I go about doing any of this. Could you walk me through it I have 3 more questions like it

jtug6 · Answer

Well solve for y for eqn 1. Add 3x to both sides perhaps? What does that give you for -3x + y = 1 if you add 3x to both sides?

saadi101 · Answer

I don't understand explaining this in text, could you write out what your doing?

jtug6 · Answer

$$-3x + y = 1$$

and we're adding 3x to both sides

jtug6 · Answer

$$-3x + 3x + y = 1 + 3x$$ right?

saadi101 · Answer

okay, yea

jtug6 · Answer

so now you have $$y = 1 + 3x $$ because -3x + 3x cancel right?

saadi101 · Answer

right

jtug6 · Answer

Now you know what y is, right? Well we have a 2nd equation which is:
$$4x + y = 8$$

jtug6 · Answer

So, if we know what y is what can we do to that equation?

jtug6 · Answer

We're doing substitution, yes?

saadi101 · Answer

right

jtug6 · Answer

We know that y was equal to 1 + 3x so y has a new meaning too. It isn't just y anymore. We're substitution the what into y for $$4x +  y = $$

jtug6 · Answer

err $$4x + y = 8$$

saadi101 · Answer

okay....

jtug6 · Answer

Ok here i'll try to make it easier xD|dw:1454818354836:dw|