Question

HURRYYYYYWhat is the first term in the sequence for which d = -2 and a7 = 3?

Answer 1

Answer:

$a_1=15$

Step-by-step explanation:

We are talking about arithmetic progression.

Using the formula:

$a_n=a_1+(n-1) \cdot d$

$a_7=a_1+(7-1) \cdot d$

$3=a_1+(7-1) \cdot (-2)$

$3=a_1+(6) \cdot (-2)$

$3=a_1-12$

$a_1=15$

Answer 2

Answer:

$\huge \boxed{a_1=15 }}$

Step-by-step explanation:

Using the nth term formula:

$a_n=a_1+dn-d$

$a_7=3 \\ \\ n=7 \\ \\ d=-2$

$3=a_1+-2(7)-(-2)$

Simplifying and solving for the first term.

$3=a_1-14+2$

$3=a_1-12$

$15=a_1$

The first term of the sequence is 15.