$\sqrt{1.8 \times \sin(46 ) \div 7.8 {}^{2} } - 50.8 \\ \sqrt{1.8} \times 0.72 \div 60.84 - 50.8 \\ \sqrt{1.29 \div 10.04 } \\ \sqrt{0.128 } \\ 0.358$

8 0

2 years ago

The third term in an arithmetic sequence is 9 and the fifth term is 21 . If the first term if a1, which is an equation for the n

tino4ka555 [31]

Answer:

A: an = 6n - 9

Step-by-step explanation:

third term in an arithmetic sequence is 9

a3 = a + 2d

a + 2d = 9

the fifth term is 21

a5 = a + 4d

a + 4d = 21

a + 2d = 9 (1)

a + 4d = 21 (2)

Subtract (1) from (2) to eliminate a

4d - 2d = 21 - 9

2d = 12

d = 12/2

d = 6

Substitute d = 6 into (1)

a + 2d = 9 (1)

a + 2(6) = 9

a + 12 = 9

a = 9 - 12

a = -3

nth term of this sequence = a + (n - 1)d

= -3 + (n - 1)6

= -3 + 6n - 6

= 6n - 9

an = 6n - 9

3 0

2 years ago