If makes positive intercept of 2 and 0 unit on and axis respectively and enclose an area of square units with the -axis, find .
It is given that lies above the -axis in the interval .
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As per the question ∫ 0 2 f ( x ) d x = 4 3
We can also evaluate the above integral using integration by parts:
∫ 0 2 1 . f ( x ) d x = f ( x ) . ∫ 0 2 1 d x − ∫ 0 2 f ′ ( x ) . x d x
Hence ∫ 0 2 x f ′ ( x ) d x = f ( x ) . ∫ 0 2 1 d x − ∫ 0 2 f ( x ) d x
= [ x f ( x ) ] 0 2 − 3 / 4
= [ 2 f ( 2 ) − 0 f ( 0 ) ] − 3 / 4
= [ 2 ∗ 0 ] − 3 / 4
S i n c e f ( 2 ) = 0
= − 3 / 4