A system of equations is set up to determine the number of nickels and the number of quarters that Elissa has. Which ordered pair does not represent a valid solution to this system?

A system of equations 3x - y = 7 and x - 2y = 4 is set up to determine the number of nickels and the number of quarters that Elissa has. Which ordered pair does not represent a valid solution to this system?

a. (2,-1)

b. (3,2)

Answer;

(3,2) is not a valid solution to the system

Explanation;

Given

3x - y = 7

x - 2y = 4

To get the ordered pair that represent a valid solution, we have to substitute the values of x and y in the above function.

For (2,-1)

The test goes thus;.

By substituton; 3x - y = 7 becomes

3(2) - -1 = 7

6 + 1 = 7

7 = 7

By substituton; x - 2y = 4 becomes

2 - 2(-1) = 4

2 + 2 = 4

4 = 4

So, (2,-1) is a valid solution.

We perform the same test on the second option.

For (3,2)

The test goes thus;.

By substituton; 3x - y = 7 becomes

3(3) - 2 = 7

9 - 2 = 7

7 = 7

By substituton; x - 2y = 4 becomes

3 - 2(2) = 4

3 - 4 = 4

-1 ≠ 4

So, (3,2) is not a valid solution.

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