To evaluate the combination we proceed as follows:
21C3
Given nCk we shall have:
n!/[(n-k)!k!]
thus plugging the values in the expression we get:
21!/[(21-3)!3!]
=21!/(18!×3!)
=1330
Answer: 1330
<span>x intercept when f(x) = 0
so
</span><span>x^2-81 = 0
x^2 = 81
x = + 9 and x = -9
Answer
</span><span>C -9</span>
Answer:
16
Step-by-step explanation:
8*2
Answer: 
Step-by-step explanation:
By definition, the perimeter of a rectangle is:

Where "l" is the lenght and "w" is the width.
If you solve for "l":

In this case, you know that the following expression represents the perimeter of the rectangle:

And the width of that rectanle is represented wih this expression:

Therefore, based on the explained above, you can conclude that the lenght of that rectangle is given by:

Finally, simplifying the expression, you get:
