if a is a positive integer , and if the units digit of a ^ 2 is 9 and the units digit of ( a + 1 ) ^ 2 is 6 , what is the units digit of ( a + 2 ) ^ 2 ?
"if the units digit of a ^ 2 is 9 , then the units digit of a is either 3 or 7 . if the units digit of ( a + 1 ) ^ 2 is 6 , then the units digit of a + 1 is either 4 or 6 . to satisfy both conditions , the units digit of a must be 3 . then a + 2 has the units digit of 5 , thus the units digit of ( a + 2 ) ^ 2 will be 5 . the answer is c ."
power(add(multiply(9, 2), 2), 2)