Positive integers , and , where and are coprime integers and is a prime, satisfy the equation above. Find .
Notation: denotes the constant of integration .
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
I = ∫ ( x − 3 ) 2 ( x − 4 ) 2 d x = ∫ ( x − 3 2 + ( x − 3 ) 2 1 − x − 4 2 + ( x − 4 ) 2 1 ) d x = 2 ln ( x − 3 ) − x − 3 1 − 2 ln ( x − 4 ) − x − 4 1 + C = 2 ln ( x − 4 x − 3 ) + 1 − x − 3 1 − 1 − x − 4 1 + C = ( 1 − x − 3 1 ) + ln ( x − 4 x − 4 + 1 ) 2 − ( 1 + x − 4 1 ) + C = ( 1 − x − 3 1 ) + ln ( 1 + x − 4 1 ) 2 − ( 1 + x − 4 1 ) + C By partial fractions decomposition – see below where C is the constant of integration.
⟹ p + q + r = 3 + 2 + 4 = 9
Note: Assuming that (reference: Partial Fractions - Repeated Factors )
Let ( x − 3 ) 2 ( x − 4 ) 2 1 = x − 3 A + ( x − 3 ) 2 B + x − 4 C + ( x − 4 ) 2 D . Multiplying both sides by ( x − 3 ) 2 ( x − 4 ) 2 and flipping sides.
A ( x − 3 ) ( x − 4 ) 2 + B ( x − 4 ) 2 + C ( x − 3 ) 2 ( x − 4 ) + D ( x − 3 ) 2 ⟹ B ⟹ D − 4 A + 4 B − 2 C + D ⟹ 2 A + C 2 A + B + 4 C + 4 D ⟹ 2 A + 4 C ⟹ C ⟹ A = 1 = 1 = 1 = 1 = 2 . . . ( 1 ) = 1 = − 4 . . . ( 2 ) = − 2 = 2 Let x = 3 Let x = 4 Let x = 2 Let x = 5 ( 2 ) − ( 1 ) Substitute in ( 1 )