The cube root of 1000 (one thousand) equals exactly 10. There is no other number that when, multiplied by itself twice, will equal 1000.
10 times 10 times 10 = 1000.0000
9.9999 times 9.9999 times 9.9999 = 999.9700
10.0001 times 10.0001 times 10.0001 = 1000.0300
The cube root of 1000 (or any other number) can be designated by using the radical sign (modified capital letter V with shortened leg on the left leg of the V and a horizontal line sufficiently long to accommodate the number extending to the right), inserting the number 1000 (or other) under the line (in the box so to speak) and placing a small 3 (to designate cube root) within the notch of the V. A V-notch without a number is understood to designate square root, a V-notch with a number 4 designates the fourth root, etc.
For Yahoo! Answers, it is best to designate the cube root of a number x as x^1/3 (square root would be designated as x^1/2 and other roots designated as ^1/4 for fourth root, ^1/5 for fifth root, etc.).
We all know that it is much easier to draw this radical and its associated numbers than it is to describe how to do it!
參考: Multi-year bordering on Mega-year experiences with numbers.
Clearly 10 is a cube root. So factorising the left hand side we get:
(x - 10) (x^2 + 10x + 100) = 0
We can factorise the second factor here by 'completing the square', the standard way of solving quadratic equations. We get
(x + 5)^2 + 75 = 0 and therefore
(x + 5)^2 = -75
No square of a real number can be negative, but if we introduce complex numbers where 'i' is defined to be the square roote of -1, we can proceed to solve the equation. We can write -75 as (sqrt(75)i)^2. Thus
(x + 5)^2 = (sqrt(75)i)^2
Taking the square root of each side and introducing plus or minus on the right hand side (since (-z)^2 = (z)^2 for all complex z),
x + 5 = sqrt(75)i or -sqrt(75)i or
x + 5 = 5 sqrt(3) i or -5 sqrt(3) i giving
x = -5 (1 + sqrt(3)i) or -5 (1 - sqrt(3)i)
which gives the final two solutions. We thus have three solutions to your question which is the maximum has a cubic polynomial can have at most three roots.