# Pre-Calc

Solve the system of equations using either the substitution method or the multiplication/addition method

3x+2y=14
2x-4y=4

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1. I would double the first then add that to the 2nd to get
8x = 32
x =4
sub into the first:
12 + 2y = 14
2y = 2
y = 1

x=4, y =1

check by subbing those values into both equations, they should work

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posted by Reiny
2. thanks so much! do you know how i could check the solution by writing the system as a matrix equation and using the inverse matrix?

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3. Wow , that would be overkill, but anyway ....

first of all , it is very difficult to write it in matrix form in this format,
so you would have the matrix
3 2
2-4 multiplied by the column matrix
x
y
=
14
4

I will assume you know how to find the inverse of a 2by2 matrix, and how to multiply matrices
the inverse of our 2by2 is
1/4 1/8
1/8 -3/16

so
1/4 1/8
1/8 -3/16
multiplied by
14
4
gives us
4
1

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posted by Reiny
4. ahh thank you and sorry for the overkill

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