Question

Choose the correct option for the following.
(-1) x (-1) x (-1) x (-1) x ... 80 times = ___

• A. 1
• B. -1
• C. 80
• D. -80

Answer 1

The correct option is A 1

When even number of negative integers are multiplied together, the product will always be a positive integer.

For example:
(-1) x (-1) = +1 [2 negative integers are multiplied]

(-2) x (-2) x (-3) x (-4) = +48 [4 negative integers are multiplied]

But, (-1) x (-1) x (-1) = -1
[3 negative integers are multiplied i.e, the number of negative integers is odd, so the product will be a negative integer]

Given: (-1) x (-1) x (-1) x (-1) x ... 80 times
Here we are multiplying (-1) x (-1)... 80 times.
$\therefore$ The product will be positive.
$\Rightarrow$ 1 x 1 x 1 x 1 x ... 80 times = +1