Question

Which of the following equations could be used to solve for the tenth term of the following sequence? 15, 13, 11, 9, ...

a) A(10) = 15 + 10(-2)
b) A(10) = 15 + 9(-2)
c) A(10) = 15 + 9(2)
d) A(10) = 15 + 10(2)

Answer 1

Equations that could be used to solve for the tenth term of the sequence:

15, 13, 11, 9, ... is

b) A(10) = 15 + 9(-2)

Explanation:

We are given a sequence:

15,13,11,9,...

The above sequence is an arithmetic progression with

first term=A(1)=15 and common difference=d=-2

Now, the nth term of an arithmetic progression is determined by the formula

A(n)= A(1)+(n-1)d

⇒ A(10)= 15+9(-2)

Hence, the correct option is:

b) A(10) = 15 + 9(-2)

Answer 2

b) A(10) = 15 + 9(-2)

Explanation

15, 13, 11, 9, ... This is an arithmetic sequence.

The common difference = 13 - 15 = -2

or = 9 - 11 = -2

The first term of the sequence = 15.

The nth term of an arithmetic sequence is given by:

Tn = a + (n - 1)d

∴ T₁₀ = 15 + (10 - 1)(-2)

= 15 + (9 × -2) ⇒ This is the expression you need.

= 15 + -18

= -3