1) the nth term of a sequence is 25-3n
a) work out the first three terms.
b) work out the value of the first negative term.

see explanation

Step-by-step explanation:

To find the first 3 terms substitute n = 1, 2, 3 into the formula

(a)

= 25 - (3 × 1) = 25 - 3 = 22

= 25 - (3 × 2) = 25 - 6 = 19

= 25 - (3 × 3) = 25 - 9 = 16

The first three terms are 22, 19, 16

Note the difference between consecutive terms is - 3

19 - 22 = 16 - 19 = - 3

Continuing this pattern

(b)

16 - 3 = 13

13 - 3 = 10

10 - 3 = 7

7 - 3 = 4

4 - 3 = 1

1 - 3 = - 2

The first negative term is - 2

John sold 30U

Rick sold 25U

So, Rick sold 5 fewer units than John.

Hope that helps.