Question

Which of the following is not an A.P

a, 2a, 3a, 4a ........

B 2, 5/2, 3, 7/2, ......

C 1.2, -3.2, -5.2, -7.2, .........

D 2, 4, 8, 16,......

Answer 1

Answer:

Option c and d

Step-by-step explanation:

For option a:-

2a , 3a , 4a ...

Let a be any number such as 6

Therefore ...

2*6 , 3*6 , 4*6 ...

12 , 18 , 24 ...

D = 18-12 = 24 -18

D = 6 = 6

Hence it is an AP because D is a constant

For option b:-

2 , 5/2 , 3 , 7/2 ...

It can also be written as...

2 , 2.5 , 3 , 3.5 .....

D = 2.5 - 2 = 3 - 2.5

D = 0.5 = 0.5

Hence it is an AP because D is a constant

For option c:-

1.2 , -3.2 , -5.2 , -7.2 ....

D = 1.2 - (-3.2) = -5.2 - (-3.2)

D = 1.2 + 3.2 = -5.2 + 3.2

D = 4.4 ≠ -2

Hence it is not an AP because D is not a constant

For option d:-

2 , 4 , 8 , 16 ...

D = 4 - 2 = 8 - 4

D = 2 ≠ 4

Hence it is not an AP because D is not a constant

Therefore ...

c and d and not an AP

Hope it helps

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