Solving Multi-Step Equations in One Variable

Method

Solving Multi-Step Equations

When solving equations, sometimes more than one step is needed. Both the number of steps and the operations required depend on the complexity of the given equation. For example, consider the following pair of equations.

rl Equation (I):& 3/2(x-2)+5 = 14 [0.8em] Equation (II):& y+2y-4 = 11-2y

The general idea is to simplify both sides of the equation and then isolate the variable on one side of the equation. This is usually done by collecting all the variable terms on one side of the equations and combining them. Then, the operations applied to the variable are undone in reverse order.

Solving Equation (I)

Equation (I) contains a fraction and parentheses. 3/2(x-2)+5=14

1
Clear Parentheses and Combine Like Terms on Each Side
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Apply the Distributive Property to clear the parentheses on the left-hand side of the equation. In this case, distribute 32 to each term inside the parentheses. Then, combine like terms on the left-hand side.

3/2(x-2) + 5 = 14
3/2x- 3/2* 2 + 5 = 14
3/2x-3+5=14
3/2x+2=14

2
Isolate the Variable
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Apply the Properties of Equality to isolate the variable on one side of the equation. In this case, first apply the Subtraction Property of Equality.

3/2x+2=14
3/2x+2-2=14-2
3/2x=12

The coefficient of the variable is a fraction. The Multiplication Property of Equality can be used to multiply both sides of the equation by the reciprocal of the coefficient.

3/2x=12
3/2x*2/3=12*2/3
3/2*2/3* x=12*2/3
1* x = 12*2/3
x = 12*2/3
x=12*2/3
x = 24/3
x=8

As such, x=8 is the solution of Equation (I).

Solving Equation (II)

In this equation, the variable is on both sides of the equation. y+2y-4=11-2y Solving the equation will require the additional step of collecting the variables on one side of the equation.

1
Clear Parentheses and Combine Like Terms on Each Side
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Apply the Distributive Property to clear the parentheses on each side of the equation. There are no parentheses to clear in this equation, so start by combining like terms instead.

y + 2y - 4 = 11-2y
3y - 4 = 11-2y

2
Collect the Variable on One Side of the Equation
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Apply the Properties of Equality to collect all the variables on one side of the equation. In this case, add 2y to both sides of the equation to group the y-terms on the left-hand side.

3y - 4 = 11-2y
3y - 4 + 2y = 11
3y + 2y - 4 = 11-2y+2y
5y - 4 = 11

3
Isolate the Variable
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Apply the Properties of Equality again to isolate the variable on one side of the equation. In this case, add 4 to both sides, then divide both sides of the equation by 5.

5y - 4 = 11
5y = 11+4
5y=15
y = 15/5
y = 3

In conclusion, y=3 is the solution of Equation (II).

Note that the operations used to solve Equations (I) and (II) may not be the same as those required to solve a different equation.

Exercises
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