How to use it
- Recognize two perfect squares separated by subtraction.
- Take each square root.
- Write the product of sum and difference.
See it in action
101²−99²=(101−99)(101+99)=2×200=400.
How to verify it
Direct squares: 10201−9801=400.
Spot a Difference of Squares
The identity a²−b²=(a−b)(a+b) turns some hard products and factorizations into easy ones.