What is the greatest prime factor of 42^2+75^2+6300 Options
A) 3 B) 7 C) 11 D) 13 E) 79
42^2 = (50-8)(50-8) = 1764   75^2 = (100-25)(100-25) = 5625   1764+5625+6300= 
<gadget id="calculator">1764+5625+6300</gadget>
<output>13_689</output>
13689   this number is divisible by 3 and 9   divide by 9 and get 1521, the sum of this number is again a multiple of 9, thus we can divide it one more time by 9. we get 169, and 169 is 13^2. thus the answer is 13.   ANSWER:13
<result>D</result>
What is the greatest prime factor of 42^2+75^2+6300