Idea 12of 23Builds onEquals means the same value
Do the same to both sides
How can you change an equation and keep it true?
Today you'll discover
- what happens if one side changes
- the move that keeps it level
- how to get x alone
Think firstx + 3 = 11: the pans are level
You take 3 off the left pan only. What happens?
Decide first, then press Next. Watch whether the pans stay level.
A level pan balance: a box marked x and a 3 block on the left, an 11 block on the right. Taking 3 off the left only tips it toward the right. Taking 3 off both pans keeps it level, leaving x against 8. Putting 8 back in the box gives 8 + 3 = 11 on both sides. The last step shows x + 9 = 25.
See the whole ideathe big idea and the key word, in one place
The big idea
Do the same to both sides of an equation, and it stays true.
Keep it level
Each move is done to both sides.
- startx + 3 = 11
- − 3 from bothx = 11 − 3
- solvedx = 8
Easy to get wrongTaking from one side only tips the balance: the equation is no longer true.
Key word
- solve
- find the value of the letter that makes an equation true
Ready to use it?
- Choose the move that keeps an equation balanced.