Is #x=7# a solution to #x^4+3x^3-21x+7#?

1 Answer
Burglar
May 26, 2016

No, it is not.

Explanation:

I assume that you want to know if #x=7# is solution of
#x^4+3x^3-21x+7=0#. In fact to have a solution you need to have an equation, not a simple polynomial.

To find if it is a solution, it is enough to substitute and verify if the result is zero.

#7^4+3*7^3-21*7+7=2401+1029-147+7=3290#.
Then #x=7# is not a solution.

Actually this equation has two real solutions #x\approx 0.33956# and #x\approx 1.8814#.

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