M4.8.6 For the adult
Two equations: substitution
One equation says y = 2x + 1. How do I use that in 3x + y = 11?
What this chapter teaches
When one equation gives a letter in terms of the other, put it in place of that letter, in brackets, and solve. Then find the other letter and check in both equations.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why does the expression go in brackets when you substitute it?
- What do you do if neither equation has a letter on its own?
- How can you check a pair of answers?
After the chapter, the learner can
- Solve two equations by putting one into the other
- Check an answer in both equations
What they copy into their notebook
Put one equation into the other, in brackets. Solve for one letter, find the other, then check in both equations.