Asked by Emily
Solve the equation x^3 - 2x + 4 = 0.
==> I know the answer is -2, but I can't seem to remember how to solve these by hand without using a graphing calculator. Any help is greatly appreciated!! :)
==> I know the answer is -2, but I can't seem to remember how to solve these by hand without using a graphing calculator. Any help is greatly appreciated!! :)
Answers
Answered by
Reiny
Unless they factor, cubic equations cannot be easily solved "by hand"
In this case, try subbing ±1 and ±2 into the equation to get a zero.
You were right to find that x = -2 works
so (x+2) must be a factor.
Use long algebraic division or synthetic division to find the other factor to be (x^2 - 2x + 2)
using the quadratic formula on
x^2 - 2x + 2 = 0 gives me two complex roots, namely (1 ± i)/2
In this case, try subbing ±1 and ±2 into the equation to get a zero.
You were right to find that x = -2 works
so (x+2) must be a factor.
Use long algebraic division or synthetic division to find the other factor to be (x^2 - 2x + 2)
using the quadratic formula on
x^2 - 2x + 2 = 0 gives me two complex roots, namely (1 ± i)/2
Answered by
Reiny
the two complex roots should have been just
1 ± i
1 ± i
Answered by
Emily
Ohhh I see. Thanks Reiny this helped a lot!! :)
There are no AI answers yet. The ability to request AI answers is coming soon!
Submit Your Answer
We prioritize human answers over AI answers.
If you are human, and you can answer this question, please submit your answer.