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Lv 4
? asked in Science & MathematicsMathematics · 1 decade ago

Another algebra question?

Can you check my work please? I am not sure if I have done this correctly. I am solving systems of equations using subtraction.

x-2y=14 x+3y=9

I have to isolate x.

x=14-2y

Now I have to substitute this expression for y in the other equation.

(14-2y)+3y=9

Now I have to subtract 14 and 2.

12y+3y=9

Now I think I add 12 and 3 together because they are alike.

15=9

I don't think this is correct. I did it the other way around and I got 10=14.

I think I might have to switch the signs around, so I would subtract 3 from 12 instead of adding. But this might be right because there are 2 types of solutions, No Solution, and Infinitely many solutions. Solutions.

Thank you.

Update:

I meant substitute the expression for x

1 Answer

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  • KeplJoey
    Lv 7
    1 decade ago
    Favorite Answer

    Error in the very first line!

    Isolating x in the first equation gives x = 14 + 2y (Not 14 - 2y)!

    See where that takes you.

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