Substitution Method - JSS3 Mathematics Lesson Note

In the substitution method, one equation is solved for one variable in terms of the other and substituted into the second equation.

Example:

Using the same equations:

2𝑥+3𝑦=8

4𝑥−2𝑦=2

Step 1: Solve the first equation for 𝑥:

2𝑥=8−3𝑦

𝑥=8−3𝑦

 Step 2: Substitute 𝑥 into the second equation:

4(8−3𝑦^2)−2𝑦=2

4(4−3𝑦^2)−2𝑦=2

16−6𝑦−2𝑦=2

16−8𝑦=2

−8𝑦=−14

𝑦=14/8=1.75

Step 3: Substitute 𝑦 back into 𝑥=8−3𝑦/2  to find 𝑥:

𝑥=8−3(1.75)/2

𝑥=8−5.25/2

𝑥=2.75/2

𝑥=1.375

Thus, 

𝑥=1.375 and 𝑦=1.75 are again the solutions.