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Equations

Find solutions from a replacement set

The solution is the number or numbers that make an equation true.

Find the solution of the following equation if the replacement set is {0, 1, 2, 3}.

4n – 7 = 5

0
1
2
3

Solution:

Take each number from the replacement set, plug it into the equation, and simplify.

You will find that only the number 3 makes the equation true.

4n – 7  =  5

4(3) – 7
 ? =
5 Plug in n = 3

12 – 7
 ? =
5 Multiply

5  =  5 Subtract

In contrast, all the other numbers in the replacement set make the equation false. For example, try the number 2.

4n – 7  =  5

4(2) – 7
 ? =
5 Plug in n = 2

8 – 7
 ? =
5 Multiply

1  ≠  5 Subtract

Since the equation is true when you plug in 3, the solution is 3.

Find the solution of the equation -3 = $\frac{9}{y}$ if the replacement set is {-5, -4, -3, -2}

-5
-4
-3
-2