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Mathematics 18 Online
OpenStudy (anonymous):

Which equation shows the substitution method being used to solve the system of linear equations? x + y = 6 x = y + 5 A.(y + 5) + y = 6 B.x = (x – 6) + 5 C.x + y = y + 5 D.x + (y + 5) = 6 The system of equations is inconsistent. What are the missing values? 5x + ___y=2 ___x+3y=8 please help will fan and medal

OpenStudy (solomonzelman):

if you know what a substitution method is, then you should be able to tell me. (Hint: you are substituting "y+5" instead of x, based on our second equation)

OpenStudy (solomonzelman):

(and substituting this, into the 1st equation)

OpenStudy (anonymous):

i dont really get substitution method

OpenStudy (solomonzelman):

okay, we can go through an example. lets say you have a system below: \(\large\color{black}{ a+b=7 }\) \(\large\color{black}{ a=b+5 }\) what you do is you substitute, \(\large\color{black}{ b+5 }\) instead of a, like this. \(\large\color{black}{ \color{red}{a}+b=7 }\) \(\large\color{black}{ \color{red}{b+2}+b=7 }\)

OpenStudy (solomonzelman):

and then we are able to solve for b, right?

OpenStudy (anonymous):

yea

OpenStudy (solomonzelman):

so, in your case though, you have a different system (which is not exactly same, but very similar). \(\large\color{black}{x + y = 6 }\) \(\large\color{black}{ x = y + 5 }\) based on my example, can you tell me how you susbstitute?

OpenStudy (anonymous):

so you substitute y+5 instead of x?

OpenStudy (solomonzelman):

yes

OpenStudy (solomonzelman):

and which of the options will this substitution give us?

OpenStudy (anonymous):

A?

OpenStudy (solomonzelman):

yes, there you go!

OpenStudy (anonymous):

yay! lol and could you help me with the second one?

OpenStudy (solomonzelman):

surely...

OpenStudy (anonymous):

The system of equations is inconsistent. What are the missing values? 5x + ___y=2 ___x+3y=8

OpenStudy (anonymous):

i didnt really get this one

OpenStudy (solomonzelman):

I am thinking that you just have to find the value of x and the value of y, which would make the 2 equations into parallel lines (but should not be the same exact line).

OpenStudy (solomonzelman):

connection again...

OpenStudy (solomonzelman):

typically, something like this, (where a, b, c, and d, are just numbers.) \(\LARGE\color{black}{ \color{red}{a}~x+\color{blue}{b}~y=\color{darkgoldenrod}{c} }\) \(\LARGE\color{black}{\color{red}{a}~x+\color{blue}{b}~y=\color{green}{d} }\) (and in both equations a and b are same number, but c does not equal d)

OpenStudy (solomonzelman):

in your case you have: \(\LARGE\color{black}{ \color{red}{5}~x+\color{blue}{?_{_2}}~y=\color{darkgoldenrod}{2} }\) \(\LARGE\color{black}{\color{red}{?_{_1}}~x+\color{blue}{3}~y=\color{green}{8} }\)

OpenStudy (solomonzelman):

(by \(\LARGE\color{black}{ \color{blue}{?_{_2}} }\) I mean the second question, and by \(\LARGE\color{black}{\color{red}{?_{_1}} }\) I mean th first question)

OpenStudy (anonymous):

im still confused

OpenStudy (solomonzelman):

you need to set your system in a format of \(\LARGE\color{black}{ \color{red}{a}~x+\color{blue}{b}~y=\color{darkgoldenrod}{c} }\) \(\LARGE\color{black}{\color{red}{a}~x+\color{blue}{b}~y=\color{green}{d} }\)

OpenStudy (solomonzelman):

you know from the first equation, that a=5, and c=2, and from the second equation that b=3 and d=8

OpenStudy (solomonzelman):

still confused, or need time to process?

OpenStudy (anonymous):

yea im like lost

OpenStudy (solomonzelman):

okay, do you see that in your case, the blank next to x in the second equation, and 5 next to x in a 1st equation should be the same number?

OpenStudy (anonymous):

yes

OpenStudy (anonymous):

so it shoud be 5x+3y and in the second one it would be the same thing?

OpenStudy (solomonzelman):

yes

OpenStudy (solomonzelman):

So you have: \(\LARGE\color{black}{ \color{red}{5}~x+\color{blue}{3}~y=\color{darkgoldenrod}{2} }\) \(\LARGE\color{black}{\color{red}{5}~x+\color{blue}{3}~y=\color{green}{8} }\)

OpenStudy (anonymous):

thanks for your help..again lol

OpenStudy (solomonzelman):

if you subtract the 2 equations the left side is going to be zero, and the right is -6, and you know that 0 doesn't equal to -6. there is the inconsistency.

OpenStudy (solomonzelman):

yw

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