3.2-Substitution Method
3.2-Substitution Method Important Formulae
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Grade 10 → Math → Pair of Equations in Two Variables → 3.2-Substitution Method
- Use the most appropriate algebraic method in order to solve the given pair of linear equations.
The substitution method is a powerful technique used to solve a pair of linear equations in two variables. This method involves expressing one variable in terms of the other and then substituting it into the second equation. This approach simplifies the equations, making it easier to find the values of the variables.
1. Steps to Solve Using the Substitution Method
To solve a pair of equations using the substitution method, follow these steps:
- Step 1: Start with the given pair of equations. For example:
- Step 2: Solve one of the equations for one variable. Here, we can solve equation (2) for $x$:
- Step 3: Substitute this expression into the other equation (1):
- Step 4: Simplify and solve for the remaining variable:
- Step 5: Substitute the value of $y$ back into the equation for $x$:
- Step 6: State the solution as an ordered pair $(x, y)$:
$$\begin{align*} (1) \quad 2x + 3y &= 12 \\ (2) \quad x - y &= 1 \end{align*}$$
$$x = y + 1$$
$$2(y + 1) + 3y = 12$$
$$2y + 2 + 3y = 12$$
$$5y + 2 = 12$$
$$5y = 10$$
$$y = 2$$
$$x = 2 + 1 = 3$$
$$\text{Solution: } (3, 2)$$
2. Example Problem
Let's look at another example:
Consider the equations:
$$\begin{align*} (1) \quad 3x + 4y &= 24 \\ (2) \quad x - 2y &= 1 \end{align*}$$Using the substitution method, we can solve this step by step:
- From equation (2), express $x$ in terms of $y$:
- Substitute this expression into equation (1):
- Simplify:
- Now, substitute $y$ back to find $x$:
$$x = 2y + 1$$
$$3(2y + 1) + 4y = 24$$
$$6y + 3 + 4y = 24$$
$$10y + 3 = 24$$
$$10y = 21$$
$$y = 2.1$$
$$x = 2(2.1) + 1 = 5.2$$
The solution is:
$$\text{Solution: } (5.2, 2.1)$$
3. Key Points to Remember
- The substitution method is especially useful when one equation can be easily manipulated to express one variable in terms of the other.
- Always check the solution by substituting the values back into both original equations to verify correctness.
- This method can also be applied to nonlinear equations, but it may require more complex algebraic manipulation.
4. Advantages of the Substitution Method
The substitution method has several advantages:
- It provides a clear and systematic approach to solving equations.
- This method is particularly helpful when dealing with equations where one variable is already isolated or easily isolatable.
- It can simplify problems that might be more complicated if tackled using other methods like elimination.
5. Practice Problems
To gain proficiency in the substitution method, try solving the following pairs of equations:
- 1. $x + y = 10$ and $2x - y = 4$
- 2. $5x + 3y = 15$ and $y = x + 2$
- 3. $x - 3y = -6$ and $4x + y = 20$
By practicing these problems, you will enhance your understanding and application of the substitution method in solving linear equations.