Problem Solving (PS) | Re: If a is a positive integer, and if the units digit of a^2 is 9 and the

JeffTargetTestPrep

I reached the same answer with the following strategy, can you please confirm if this method is valid ?
since a^2 =9 [equation 1], (a+1)^2=4 [equation 2], (a+2)^2=? [equation 4];

from 2: [ a^2 + 2 (a*1) +(1)^2] =4,
from 1 into 2:
[9+ 2a+1] =4
10 + 2a=4;
2a=-6
a=-3 [equation 3]
from 3 into 4
(a+2)^2 =(-3+2)^2=(-1)^2=1

Statistics : Posted by mohamedanter • on 10 Feb 2011, 15:56 • Replies 19 • Views 41571

---