Problem
ALG-B1-M02-P004 Difference of Square Blocks
#4
★☆☆☆☆ Level 1 of 5
Factor \( (2a+b)^2-(a-2b)^2 \).
Use \(U^2-V^2=(U-V)(U+V)\).
Let \(U=2a+b\), \(V=a-2b\). Then \(U-V=a+3b\), \(U+V=3a-b\).
Thus the expression equals \((a+3b)(3a-b)\).
The key is not to expand the squares too early.