Answer:
1000
Step-by-step explanation:
12
x^2 - a
If a is a perfect square we could factor
x^2 - b^2 = (x-b)(x+b)
So a cannot be 36,49,81 since they are perfect squares
a must be 12
2) 11
3) 21
4) 7
2) (-6) -(-17) = 17 - 6 = 11
3) 19 - (-2) = 19 + 2 = 21
4) (-13) + 20 = 20 - 13 = 7
