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1 year ago

2. Find the 20th term of an arithmetic sequence if its 6th term is 14 and 14th term is 6.

Mathematics

2 answers:

Fudgin [204]1 year ago

8 0

Answer:

$\sf t_{20}= 0$

Step-by-step explanation:

<h3>Arithmetic sequence:</h3>

$\sf \boxed{\bf n^{th} \ term = a + (n-1)d}\\\\\text{Here, a is the first term ; d is the common difference }$

6th term is 14 ⇒ $\sf t_6 = 14$

a + (6 - 1)d = 14

a + 5d = 14 --------------(I)

14th term is 6 ⇒ $\sf t_{14} = 6$

a + (14-1)d = 6

a + 13d = 6 ----------------(II)

Subtract equation (II) from equation(I)

(I) a + 5d = 14

(II) a + 13d = 6

-8d = 8

d = 8 ÷(-8)

$\sf \boxed{\bf d= (-1)}$

Plugin d = -1 in equation (I)

a + 5(-1) = 14

a -5 = 14

a = 14 + 5

$\sf \boxed{\bf a = 19}$

20th term:

$\sf t_{20}= 19 + 19*(-1)$

= 19 - 19

$\sf \boxed{\bf t_{20} = 0}$

kap26 [50]1 year ago

7 0

Answer:

Step-by-step explanation:

The number of terms of an Arithmetic progressions has the formular.

Tn = a + ( n - 1 ) d

From the question,

6th term = 14

14th term = 6

Therefore,

a + 5d = 14 -----------(1)

a + 13d = 6 ----------(2)

subtracting

-8d = 8

dividing bothsides by -8

$\frac{ - 8d}{ - 8} = \frac{8}{ - 8} \\ d = - 1$

Therefore,

common difference= -1

substituting the value of d into equation (1)

a + 5 ( -1) = 14

a - 5 = 14

a = 14 + 5 = 19

First term = 19

For the 20th term

T 20 = a + 19d

19 + 19 ( -1 )

19-19 = 0

Therefore,

20th term = 0

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