When 125 is added to a number, it becomes a perfect square. When 176 is added to that same number, it also becomes a perfect square. What is the number?
a^2 - b^2 = ([176+ n] - [125 +n])
a^2 - b^2 = 176 - 125
a^2 - b^2 = 51
Note that if a =10 and b = 7 this is true because 10^2 - 7^2 = 100 - 49 - 51
So a^2 = 100 and b^2 = 49
So
100 - 176 = n = -76
49 - 125 = = n = -76
So....the number is -76
Another way to do this problem:
x + 125 = a2 x + 176 = b2
x + 176 = b2 x + 125 = a2
Subtracting the first equation from the second: 51 = b2 - a2
factoring: 17·3 = (b + a)(b - a)
This means that b = 10 and a = 7
So: x + 125 = a2 ---> x + 125 = 72 ---> x + 125 = 49 ---> x = -76
x + 176 = b2 ---> x + 176 = 102 ---> x + 176 = 100 ---> x = -76