Asked by Akash
Can anybody tell me step wise step how to solve this quadratic equation?
x^3-3x^2+4=0
Please tell me step wise step as i haven't solved such type of equations before.
Thank You
x^3-3x^2+4=0
Please tell me step wise step as i haven't solved such type of equations before.
Thank You
Answers
Answered by
MathMate
Even you subject is "Quadratic Equations", the problem you submitted is a cubic equation, and there appears to be no typo.
We will solve the cubic as it is posted.
x^3-3x^2+4=0
We note that the coefficients add up to zero if we reverse the sign of x^3, i.e. (-1)-3+4=0
This indicates that x=-1 is a zero.
Use long polynomial division to reduce the equation to:
(x^3-3x^2+4)/(x+1)=x²-4x+4
which is a quadratic equation.
We can solve by factorization:
x²-4x+4 = 0
(x-2)²=0
Therefore x=-1 or x=2(multiplicity=2), i.e. x=-1, x=2 or x=2.
We will solve the cubic as it is posted.
x^3-3x^2+4=0
We note that the coefficients add up to zero if we reverse the sign of x^3, i.e. (-1)-3+4=0
This indicates that x=-1 is a zero.
Use long polynomial division to reduce the equation to:
(x^3-3x^2+4)/(x+1)=x²-4x+4
which is a quadratic equation.
We can solve by factorization:
x²-4x+4 = 0
(x-2)²=0
Therefore x=-1 or x=2(multiplicity=2), i.e. x=-1, x=2 or x=2.
Answered by
Akash
any other easy method
Answered by
MathMate
I do not see an easier method except factoring trial and error. For this particular problem, you will probably get the answers by trial factoring quite easily.
Remember that this is a cubic equation, which actually has a solution formula more complicated than the above.
There is also the Newton-Ralphson approximation method by iterations.
The above methods (factoring, long division, quadratic equation) do not introduce any algebraic operation that is beyond secondary school level.
Remember that this is a cubic equation, which actually has a solution formula more complicated than the above.
There is also the Newton-Ralphson approximation method by iterations.
The above methods (factoring, long division, quadratic equation) do not introduce any algebraic operation that is beyond secondary school level.
N+ ( n+2)=16
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