Question

Please answer with steps
In which of the following cases will the result be a negative number?
(A) - 1 + 2 - 3 + 4 -……- 19 + 20 (B) (- 1) x (-2) x ( -3) x ……x (-19) x (-20)
(C) (- 1) x (2) x ( -3) x (4)……x (-19) x (20) (D) 1 - 2 + 3 - 4 -……+ 19 – 20

Answer 1

1) First case will be positive number.

We can group the The numbers in pair.

(-1+2)+…………(-19+20)

=10*1

=10

2) In second case the answer will be positive.

Here negatives are multiplied 20 times
( even) so the answer would be positive.

3) Here negatives are multiplied 19 times, so result is negative. and last is 20

- * + = -

So the result is negative in this case.

4) Here also the results is -1

First group the terms in pairs.

So each group is -1

= -1 * 10

= -10

hope helped!