Test 6 Section 4- #4 (page 713)

Do some plug-in to figure out what they want:  

2^2 +1 = 5

3^2 + 1 = 10

4^2 +1 = 17

5^2 + 1 = 26

...and so on.

We're looking for a number that's 1 more than a perfect square.  The one that works for us is 7^2 + 1 = 49+1 = 50.  Choice E.