Find All Solutions to the Cubic Equation x³+1=0

Question

How many solutions does the equation have?

x3+1=0 x^3+1=0

Video Solution

Solution Steps

00:00 Find X
00:03 Isolate X
00:13 Extract cube root to find X
00:19 And this is the solution to the problem

Step-by-Step Solution

In the given equation:

x3+1=0 x^3+1=0 The simplest and fastest way to find the number of its solutions,

will be simply to solve it, we will do this by moving terms to isolate the unknown, then we will take the cube root of both sides of the equation, while remembering that an odd root preserves the sign of the expression inside the root (meaning - the minus sign can be taken out of an odd root):

x3+1=0x3=1/3x33=13x=13x=1 x^3+1=0 \\ x^3=-1\hspace{6pt}\text{/}\sqrt[3]{\hspace{4pt}}\\ \downarrow\\ \sqrt[3]{x^3}=\sqrt[3]{-1}\\ x=-\sqrt[3]{1}\\ \boxed{x=-1} meaning the given equation has a single solution,

therefore the correct answer is answer A.

Answer

A solution