Using Substitution to solve or check algebraic equations

Note: Always use the order of operations to solve, evaluate or compute any mathematical equation

Here is an example of an algebraic equation where you have already determined the value of x, y, and z – How should you evaluate it?

x = 15, y = 6 and z = 4.5

y2 – 2x + x – 3(z)

·        Step 1 – Rewrite the entire equation and plug the values in, remember you must put multiplication signs where needed – see where they have been added below:

62 – 2 ∙ 15 + 15 – 3 ∙ 4.5

·        Step 2 – Solve according to the order of operations

36 – 2 ∙ 15 + 15 – 3 ∙ 4.5

36 – 30 + 15 – 3 ∙ 4.5

36 – 30 + 15 – 13.5

6  +  15  – 13.5

21 –  13.5

7.5

Suppose you have an algebraic equation that you wish to solve and check; here is an example:  Solve for x

4x = 322

·        Step 1 – solve for x

4x = 322

4                  4

x = 8.5

·        Step 2 – Check your solution.  Are you correct?

Substitute your variable into the equation and check that your equation is balanced (equal on both sides of the equal sign)

4 ∙ 8.5 = 322

322 = 322

Yes it is correct!