The deposits Ginny makes at her bank each month form an arithmetic sequence. The deposit for month 3 is $150, and the deposit for month 5 is $180. Answer 1.what is common differences for each month? 2.write explicit formula for arithmetic sequence 3.amount in 12th month? 4.what month will deposit at least $500?

Question

anonymous · Answer

$$T _{n}=a+(n-1)d$$
$$T_{3}=a+2d$$
$$150=a+2d$$
$$T_{5}=a+4d$$
$$180=a+4d[1]$$
$$150=a+2d[2]$$
$$[1]-[2]$$
$$(180)-(150)=(a+4d)-(a+2d)$$
$$30=2d$$
$$d=?$$