questioner wrote:

**The only question I have about this problem is the transition from (2***a* + 2*b*)² = 100 to 2(*a* + *b*) = 10. Obviously the square root was taken but only of the (*a* + *b*)?

The square root was taken of the whole expression within the brackets, 2

*a* + 2

*b*.

So (2

*a* + 2

*b*)² = 100 yields 2

*a* + 2

*b* = 10. Then we just factor out 2: 2

*a* + 2

*b* = 2(

*a* +

*b*).