X X 's

Algebra Level 2

x 4 97 x 3 + 2012 x 2 97 x + 1 = 0 { x }^{ 4 }-97{ x }^{ 3 }+2012{ x }^{ 2 }-97x+1=0

How many values of x x satisfy the equation above?


The answer is 4.

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4 solutions

Rishabh Jain
Jan 30, 2016

Dividing the whole equation by x 2 x^2 , we get x 2 97 x + 2012 97 x + 1 x 2 = 0 \color{#3D99F6}{x^2}-\color{#D61F06}{97x}+2012-\color{#D61F06}{\frac{97}{x}}+\color{#3D99F6}{\frac{1}{x^2}}=0 P u t x + 1 x = t s u c h t h a t x 2 + 1 x 2 = t 2 2 \small{\color{#EC7300}{Put~x+\frac{1}{x}=t~such~ that~x^2+\frac{1}{x^2}=t^2-2}} t 2 97 t + 2010 = 0 \Rightarrow t^2-97t+2010=0 ( t 30 ) ( t 67 ) = 0 \Rightarrow (t-30)(t-67)=0 t = x + 1 x = 30 , 67 \Rightarrow t=x+\frac{1}{x}=30,67 x 2 30 x + 1 = 0 a n d x 2 67 x + 1 = 0 \Rightarrow x^2-30x+1=0~and~x^2-67x+1=0 Discriminant of both x 2 30 x + 1 = 0 a n d x 2 67 x + 1 = 0 x^2-30x+1=0~and~x^2-67x+1=0 is greater than 0, hence will yield two solutions each hence a total of 4 \Large \color{#69047E}{\boxed{\color{#20A900}{4}}} solutions.

Actually there is no need to find the roots,since the question only asks for the number of values,not the number of real values.Therefore,since it's a quartic equation,the number of values of x is 4

Abdur Rehman Zahid - 5 years, 4 months ago

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What about this(same question):- x 4 6 x 3 + 13 x 2 12 x + 4 x^4-6x^3+13x^2-12x+4

Rishabh Jain - 5 years, 4 months ago
Bhavana Bunsha
May 12, 2018

The degree of the equation is the number of solutions and also here nothing is said about complex or real roots so all answers are valid

Krishna Karthik
Oct 2, 2018

Lol there is a high probability of getting this question right, because the greatest number of roots a fourth degree polynomial can have is 4, and the least is 0. So, the probability of getting this question right is 1 3 \frac{1}{3} .

Tanvir Hasan
Jan 31, 2016

May be, the highest power of variable = number of solutions.

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