A) Find the 15th term of a linear sequence (AP) whose 5th term is 30 and 20th term is 75.
B) The second and the fourth terms of an exponential sequence (GP) of positive terms
are 9 and 4 respectively. Find
D) The common ratio;
i) The first term
2. Solve for x and y in the following equations: 2(x+4y) = 1.22+8y
​

A) 60

B) Common ratio, r, = 2/3

The first term, a, = 13.5

Step-by-step explanation:

A)

The formula for  the nth term of a linear sequence is an+b. So we can say:

30=5a+b

75=20a+b

which means

b=30-5a

b=75-20a

30-5a=75-20a

15a=45

a=3

30=5(3)+b

b=30-15=15

So our formula is 3n+15. Sub in 15 for n to find the 15th term: 3(15)+15=45+15=69

B)

The formula for  the nth term of an exponential sequence is arⁿ⁻¹, where a is the first term of the sequence and r is the common ratio. Therefore we can say: 9=ar, and 4=ar³, which means a=9/r and a=4/r³

9/r=4/r³

9r³=4r

9r²=4

r=√(4/9)=2/3

9=a(2/3)

a=27/2=13.5

7. d. 64

8. i. 32

9. c. 125

10. j. none of the above

11. d. 81

12. i. 216

13. e. none of the above

14. g. 240

15. e. none of the above

16. g. 32

17.   e. none of the above