Step-by-step explanation:

Answer:
a21 = -61
Step-by-step explanation:


(subtract to eliminate a₁)
9 = -3d
d = -3
-19 = a₁ + (6)(-3)
-1 = a
a21 = -1 + (21 - 1)(-3)
= -61
I find it best to switch everything exponents when taking derivatives.
F(x) = 7/x
Same as..
F(x) = 7x^-1
Take derivative..
F'(x) = -7x^-2
Plug in x = 1
F'(1) = -7(1)^-2
F'(1) = -7
Answer:
y = 20x + 40
Step-by-step explanation:
Given that the rental rate for a cement mixer has a flat rate of $40 plus $20 for each day of the rental.
That means fixed one time cost is $40 which doesn't changes with time.
If number of days is represented by "x" then rental cost for "x" days will be 20 times x or just 20x.
So the final cost will be sum of fixed cost and the rental cost per day which is:
20x+40
Now if "y" represents total rental cost over time then final cost equation can be written as:
y = 20x + 40
Hence final answer is y = 20x + 40y = 20x + 40.
Cos(x) = BC/AB = 10.5/20 = 0.525 ⇒ x = 58.3°