Solve the Exponential Equation: x^14 - x^7 = 0

Question

x14x7=0 x^{14}-x^7=0

Video Solution

Solution Steps

00:00 Find X
00:03 Factor with X to the power of 7
00:11 Take out the common factor from the parentheses
00:22 This is one solution that zeros the equation
00:26 Now let's check which solutions zero the second factor
00:30 Isolate X
00:34 1 to an odd root is always equal to 1
00:38 And this is the solution to the question

Step-by-Step Solution

The equation in the problem is:

x14x7=0 x^{14}-x^7=0

First, let's note that in the left side we can factor the expression using a common factor, the largest common factor for the numbers and letters in this case is x7 x^{7} since the seventh power is the lowest power in the equation and therefore is included both in the term with the 14th power and in the term with the seventh power, any power higher than this is not included in the term with the lowest seventh power, and therefore this is the term with the highest power that can be factored out as a common factor from all terms for the letters,

Let's continue then and perform the factoring:

x14x7=0x7(x71)=0 x^{14}-x^7=0 \\ \downarrow\\ x^{7}(x^7-1)=0

Let's continue and address the fact that in the left side of the equation we got in the last step there is a multiplication of algebraic expressions and on the right side the number 0, therefore, since the only way to get 0 from multiplication is to multiply by 0, at least one of the expressions in the multiplication on the left side must equal zero,

Meaning:

x7=0/7x=0 x^{7}=0 \hspace{8pt}\text{/}\sqrt[7]{\hspace{6pt}}\\ \boxed{x=0}

In solving the above equation, we extracted a 99th root for both sides of the equation.

(In this case, extracting an odd-order root to the right side of the equation yielded one possibility)

Or:

x71=0x7=1/7x=1 x^7-1=0\\ x^7=1\hspace{8pt}\text{/}\sqrt[7]{\hspace{6pt}}\\ \boxed{x=1}

In solving the above equation, we first isolated the variable (because it's possible..) on one side and then extracted a seventh root for both sides of the equation.

(In this case, again, extracting an odd-order root to the right side of the equation yielded one possibility)

Let's summarize then the solution of the equation:

x14x7=0x7(x71)=0x7=0x=0x71=0x=1x=0,1 x^{14}-x^7=0 \\ \downarrow\\ x^{7}(x^7-1)=0 \\ \downarrow\\ x^{7}=0 \rightarrow\boxed{ x=0}\\ x^{7}-1=0\rightarrow \boxed{x=1}\\ \downarrow\\ \boxed{x=0,1}

Therefore the correct answer is answer D.

Answer

Answers a + b