A(n) = a(n-1)+9 means that we add 9 to the previous term to get the next term. Therefore the common difference is d = 9 this sequence is arithmetic.
The first term is a(1) = 21
Plug those two values into the arithmetic formula below and simplify
a(n) = a(1) + d * [ n - 1 ]
a(n) = 21 + 9 * [ n - 1 ]
a(n) = 21 + 9*n + 9*(-1)
a(n) = 21 + 9n - 9
a(n) = 9n+12
Answer is choice D
I'll use subscript notation for brevity, i.e. 
.
By the chain rule,
We have
and
When 
, we have
and the partial derivatives take on values of
So we end up with
D
area of a rectangle = length × width
area = (2x + 3)(x - 4) ( expand using FOIL )
= 2x² - 8x + 3x - 12 = 2x² - 5x - 12 → D
Answer:
Example 11 answer = 12
Step-by-step explanation:
40, 36, 32, 28
is an arithmetic sequence.
The first term (a) is 40
The common difference (d) is -4
The formula for finding the nth term (
in an arithmetic sequence is;
= a + d(n - 1)
= 40 + -4(8 - 1)
= 40 - 28 = 12
