MCQ 11 Mark
If $a = (-1) × (-1) × (-1) ..... 100$ times and $b = (-1) × (-1) × (-1) ..... 95$ times, then $a + b =$
- A$-1$
- B$-2$
- ✓$0$
- D$1$
Answer
View full question & answer→Correct option: C.
$0$
$a = (-1) \times (-1) \times (-1) \times ...... 100$ times
Here, the number of integers in the product is even.
$\therefore a = (-1) \times (-1) \times (-1) \times ...... 100$ times
$= 1 \times 1 \times 1 \times ...... 100$ times
$= 1$
$b = (-1) \times (-1) \times (-1) \times ..... 95$ times
Here, the number of integers in the product is odd.
$\therefore b = (-1) \times (-1) \times (-1) \times ... 95$ times
$= − (1 \times 1 \times 1 \times ... 95$ times$)$
$= −1$
So,
$a + b = 1 + (-1) = 0$
Here, the number of integers in the product is even.
$\therefore a = (-1) \times (-1) \times (-1) \times ...... 100$ times
$= 1 \times 1 \times 1 \times ...... 100$ times
$= 1$
$b = (-1) \times (-1) \times (-1) \times ..... 95$ times
Here, the number of integers in the product is odd.
$\therefore b = (-1) \times (-1) \times (-1) \times ... 95$ times
$= − (1 \times 1 \times 1 \times ... 95$ times$)$
$= −1$
So,
$a + b = 1 + (-1) = 0$