Answer:
c. 
Step-by-step explanation:
We have been given that the area in square units of an expanding circle is increasing twice as fast as its radius in linear units
We will use derivatives to solve our given problem.
We know that area (A) of a circle is equal to
.
Let us find derivative of area function with respect to time.

Bring out constant:

Using power rule and chain rule, we will get:

Here
represents change is radius with respect to time.
We have been given that area of an expanding circle is increasing twice as fast as its radius in linear units. We can represent this information in an equation as:





Therefore, the radius is
and option 'c' is the correct choice.
Answer:
×
= 
Step-by-step explanation:
× 
To solve the above, we need to follow the steps below;
4k+2 can be factorize, so that;
4k +2 = 2 (2k + 1)
k² - 4 can also be be expanded, so that;
k² - 4 = (k-2)(k+2)
Lets replace 4k +2 by 2 (2k + 1)
and
k² - 4 by (k-2)(k+2) in the expression given
× 
× 
(2k+1) at the numerator will cancel-out (2k+1) at the denominator, also (k-2) at the numerator will cancel-out (k-2) at the denominator,
So our expression becomes;

Therefore,
×
= 
Answer is C only. When you increase X, the f(x) is going downwards.
5x + 4y = 32 ⇒ 45x + 36y = 288
9x - 1y = 33 ⇒ <u>45x - 5y = 165</u>
<u>41y</u> = <u>123</u>
41 41
y = 3
5x + 4(3) = 32
5x + 12 = 32
<u> - 12 - 12</u>
<u>5x</u> = <u>20</u>
5 5
x = 4
(x, y) = (4, 3)