Algebra Question #13: Inspired by Mei Li

Algebra Level 5

Find the number of integer x x satisfying ( x 2 5 x + 6 ) x 2 6 x + 8 = 1 (x^2 - 5x + 6)^{x^2 -6x +8}=1

Inspiration

Algebra Question

1 4 2 8

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4 solutions

( x 2 5 x + 6 ) x 2 6 x + 8 = 1 (x^2 - 5x + 6)^{x^2 - 6x + 8} =1 if and only if x 2 6 x + 8 = 0 = > x = 2 o r x = 4 x^2 - 6x + 8 = 0 => x = 2\ or\ x = 4 x 2 5 x + 6 = 1 = > x i s n o t a n i n t e g e r . x^2-5x+6=1 =>\ x\ is\ not\ an\ integer. For even exponent x 2 5 x + 6 = 1 = > x i s n o t a n i n t e g e r . x^2 - 5x + 6 = -1\ =>\ x\ is\ not\ an\ integer. But, using substitution, the only answer is x = 4, because if x = 2 the original equation will become 0 0 0^{0} which is not equal to 1

zero to the power zero is not defined then why does the calculator show it as 1

avn bha - 6 years, 4 months ago

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lim x -> 0 x^x = 1

Jesse Nieminen - 6 years ago

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but lim x -> 0 of 0^x = 0

both can't be right - hence undefined.

Tony Flury - 3 years ago

0^0 = 0^(a - a) = 0^a/0^a = indeterminate and not 1.

Paul Ryan Longhas - 6 years, 4 months ago

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thanks for clearing my concept !!

avn bha - 6 years, 4 months ago

9 9 = 3 i 3 i = 9 \sqrt{-9}*\sqrt{-9} = 3i*3i=-9 , but 9 9 = 81 = 9 9 \sqrt{-9*-9} = \sqrt{81} = 9 \neq-9 , so some rules have exceptions.

Whitney Clark - 6 years, 1 month ago

Since when are calculators perfect - there are plenty of examples on this site where calculators should not be trusted. Most Calculators use short cuts - which don't work in all cases : 0^0 is unsually considered to be undefined : x a = 0 : x = 0 x^a = 0 : x = 0 a x = 1 : x = 0 a^x = 1 : x = 0 so x x = ? : x = 0 x^x = ? : x = 0 which rule does one use ?

Tony Flury - 5 years, 8 months ago

Perhaps it should be 1, and is in come contexts, but it's not; and calculators make mistakes.

Whitney Clark - 5 years, 6 months ago

Calculators are not mathematicians.

Whitney Clark - 5 years, 5 months ago

Because some calculators are wrong - undefined means it could be any value - depending how you get there - lim x -> 0^ x = 0

but we also know that x^0 = 1 for non zero x - so is 0^0 = 1 or 0; there are also definitions which can make it 3 or 7 or 1 million 350 thousand or any value you want.

Tony Flury - 3 years ago

0^0 is not define

Vishal S - 6 years, 4 months ago

Did the same.

Shreyash Rai - 5 years, 6 months ago
Edwin Gray
May 13, 2018

The only possibilities are if the exponent = 0, or the argument is +/- 1. (if -1, the exponent must be even). Equating the exponent to 0 gives x =2, x= 4, However, 2 must be eliminated since the argument = 0.Equating the argument to |1| produces no integer solutions, so there is only 1. Ed Gray

The left hand side will be equal to 1 when the exponent is zero:

x 2 6 x + 8 = 0 x^{2}-6x+8=0

This has x = 2 x=2 and x = 4 x=4 as solutions.

Of course, for the left hand side to be defined, x 2 5 x + 6 x^{2}-5x+6 should NOT be zero (otherwise we would end up with 0 0 0^{0} , which is undefined), so:

x 2 5 x + 6 0 x^{2}-5x+6\neq0

This solves to x 2 x\neq2 and x 3 x\neq3

Hence our original solution cannot include the number 2, and we are left with the number 4 as a solution.

So there is just o n e \boxed{one} possible value for x x .

Ahmed Obaiedallah
Jun 12, 2015

( x 2 5 x + 6 ) x 2 6 x + 8 = 1 (x^2-5x+6)^{x^2-6x+8}=1

This will be correct only in 2 cases

1- If x 2 5 x + 6 = 1 x^2-5x+6=1\space in this case the results aren't integers

2- If x 2 6 x + 8 = 0 x^2-6x+8=0\space which will result in x = 4 a n d x = 2 x=4\space\space and \space\space x=2

In case of x = 2 \large x=2\space the equation will be 0 0 \large0^0 which is an indefinable quantity

So only if x = 4 \large\color{#D61F06}{x=4}\space that it'll be 2 0 = 1 \large\boxed{\color{#3D99F6}{2^0=1}}

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