Pointless Simplification

Algebra Level 3

n = 1 log c ( c 5 ) ( ln ( e 16 c ) 1 ( i + 1 ) 8 1 4 2 2 d x ( e π i + 2 ) 5 ) c 20 ( n = 1 6 + e π i 0 7 1 6 + ln ( e ) d x 5 ) 4 \frac{\displaystyle \sum_{n=1}^{\log_c(c^5)}\left(\dfrac{\ln(e^{16c})\cdot\frac{1}{(i+1)^8}}{\frac{1}{4}\int_{-2}^2 dx \cdot\left(e^{\pi i}+2\right)\cdot5}\right)} {\dfrac{c}{20}\cdot \left(\displaystyle \prod_{n=1}^{6+e^{\pi i}}\sqrt[5]{\int_0^7\dfrac{1}{6+\ln(e)}dx}\right)\cdot4}

Find the value of the expression above, if c c is a non-zero real number.


The answer is 5.

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1 solution

Henry U
Mar 12, 2019

x = n = 1 log c ( c 5 ) ( ln ( e 16 c ) 1 ( i + 1 ) 8 1 4 2 2 d x ( e π i + 2 ) 5 ) c 20 ( n = 1 6 + e π i 0 7 1 6 + ln ( e ) d x 5 ) 4 = n = 1 5 ( 16 c 1 ( 2 i ) 4 5 4 2 2 1 d x ) c 5 ( n = 1 5 0 7 1 7 d x 5 ) = n = 1 5 ( 16 c 1 16 5 4 4 ) c 5 ( n = 1 5 1 5 ) = n = 1 5 ( c 5 ) c 5 = 5 ( c 5 ) c 5 = 5 \begin{aligned} x &= \frac {\displaystyle \sum_{n=1}^{\log_c(c^5)} \left( \frac {\ln (e^{16c}) \cdot \frac 1{(i+1)^8}} {\frac 14 \int_{-2}^2 dx \cdot (e^{\pi i}+2) \cdot 5} \right)} {\frac c{20} \cdot \left( \displaystyle \prod_{n=1}^{6+e^{\pi i}} \sqrt[5]{ \int_0^7 \frac {1} {6+\ln(e)} dx } \right) \cdot 4} \\ &= \frac {\displaystyle \sum_{n=1}^{5} \left( \frac {16c \cdot \frac 1{(2i)^4}} {\frac 54 \int_{-2}^2 1 dx} \right)} {\frac c5 \cdot \left( \displaystyle \prod_{n=1}^{5} \sqrt[5]{ \int_0^7 \frac 17 dx } \right)} \\ &= \frac {\displaystyle \sum_{n=1}^{5} \left( \frac {16c \cdot \frac 1{16}} {\frac 54 \cdot 4} \right)} {\frac c5 \cdot \left( \displaystyle \prod_{n=1}^{5} \sqrt[5]{1} \right)} \\ &= \frac {\displaystyle \sum_{n=1}^{5} \left( \frac c5 \right)} {\frac c5} \\ &= \frac {5 \cdot \left( \frac c5 \right)} {\frac c5} \\ &= \boxed{\boxed{5}} \end{aligned}

Just in case somebody needs the LaTeX code:

\frac {\displaystyle \sum_{n=1}^{\log_c(c^5)} \left( \frac {\ln (e^{16c}) \cdot \frac 1{(i+1)^8}} {\frac 14 \int_{-2}^2 dx \cdot (e^{\pi i}+2) \cdot 5} \right)} {\frac c{20} \cdot \left( \displaystyle \prod_{n=1}^{6+e^{\pi i}} \sqrt[5]{ \int_0^7 \frac {1} {6+\ln(e)} dx } \right) \cdot 4}

Henry U - 2 years, 3 months ago

Faster method: 1. Note the factor of c/5 in the demonimator, giving a loose factor of 5 at the front of the expression 2. Look at the title 3. Assume everything else cancels out 4. Hooray! The answer is 5!

Jason Carrier - 2 years, 2 months ago

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Luckly that's not so easy in the new version, Nice method though.

Joshua Crawford - 2 years, 2 months ago

How comes (i+1)^8=(2i)^4?

A Former Brilliant Member - 2 years, 2 months ago

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( i + 1 ) 8 = ( ( i + 1 ) 2 ) 4 = ( i 2 + 2 i 1 + 1 2 ) 4 = ( 1 + 2 i + 1 ) 4 = ( 2 i ) 4 (i+1)^8 = \left( (i+1)^2 \right) ^4 = (i^2+2\cdot i \cdot 1+1^2)^4 = (-1+2i+1)^4 = (2i)^4

Henry U - 2 years, 2 months ago

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Oh, it was such a silly question!

A Former Brilliant Member - 2 years, 2 months ago

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