Ok another question...?

Question

thanks for help on the last question!! now i need some more help... so i have 6 more questions... so just bear with me if you want.

Ok this one:

x + y = 2

y = 4x +7

please just show me step-by-step how to solve it.

just dont show me the answer, i would like figure it out on my own.

thank you!!!

oh and what woulg go best here? substitution or elmination?

Answer 1

I almost always found substitution to be easier, or at least to make more sense.  Elimination has too many pieces of too many equations flying off in too many directions.  I'd get lost.  So, I'll substitute.

I can't show you the steps without showing you the answer.  But, maybe I can talk you through the steps.

The second equation is already solved for Y.  That means, we know what Y is, at least in terms of X.  We can use that to modify the first equation.

Everyplace we see Y in the first equation, we should put this thing that we know Y equals because of the second equation.

Ok, that step I'll show you.

X + ( Y ) = 2

( Y ) = ( 4X + 7 )

X + ( 4X + 7 ) = 2

From here, you simplify things until you've solved for X.

I'd suggest, adding like terms, then subtracting the same value from both sides of the equation, then dividing the same value into all terms of the equation.

Once you do that, you'll know what X is as an actual number.

Then, pick the simplest equation.  I'd pick X + Y = 2.  Put the actual number in the place of X.  Solve for Y.

That should be it.