Question

please tell fast with step - by - step explanation ​

Answer 1

(1) Given 30th term of the AP:10,7,4 is.

Answer: Option (C) : - 77

Explanation : 

Given first term a = 10,

         Last term n = 30.

         common difference d = 7 - 10 = -3.

We know that sum of n terms an = a + (n - 1) * d

                                                 a30 = 10 + (30 - 1) * (-3)

                                                         = 10 + 29 * (-3)

                                                         = 10 + (-87)

                                                        = -77.

Therefore the 30th term of the AP is  -77.

Answer 2

Answer:

-77

Step-by-step explanation:

Given:-

a1 = 10

a2 = 7

a3 = 4

To find :- a30 or the 30th term

Solution:-

an = a + (n - 1)d

Here, an = a30

a = 10

n = 30

d = ?

So, a30 = a + (30 - 1)d

a30 = a +29d

Now find d

d = a2 - a1

d = 7 - 10

d = -3

Now , a30 = ?

a30 = a + 29d

a30 = 10 + 29(-3)

a30 = 10 - 87

a30 = -77