Question

If p=1+2-3-4+5+6-7-8+...+1986, then p equals?

Answer 1

you must use AP/GP

Answer 2

@ganeshie8 @zepdrix @iGreen

Answer 3

Did you know that
1+2+3+...10= (1+10)*(10/2)=55

Answer 4

So using that we get
(1+1986)*(1986/2)=??

Answer 5

Sum = (\[Sum = \frac{ n (a + l)}{ 2 }\]
Sum = (\[Sum = \frac{ 1986 (1 + 1986)}{ 2 }\]
Sum = 1973091

Answer 6

This is because we get pairs