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Question: A function ƒ is defined by ƒ(x) = \(\frac { 1 } { 2 ^ { \mathrm { r } - 1 } }\) , \(\frac { 1 } { ...

A function ƒ is defined by ƒ(x) = 12r1\frac { 1 } { 2 ^ { \mathrm { r } - 1 } } , 12r\frac { 1 } { 2 ^ { \mathrm { r } } } < x £, r = 1, 2, 3, …… then the value of dx is equal –

A

1/3

B

1/4

C

2/3

D

1/3

Answer

2/3

Explanation

Solution

dx = dx = [2–(r–1)– 2–r]

=

= (222)\left( 2 ^ { 2 } - 2 \right) 122r\sum _ { 1 } ^ { \infty } 2 ^ { - 2 r }= 2 . 14\frac { 1 } { 4 } . 111/4\frac { 1 } { 1 - 1 / 4 } = 23\frac { 2 } { 3 }