Question

Which of the following answer choices is a solution to a²=16a. a=8b. a=-8c. a=16d. a=-4

Answer 1

This question is asking us "which number should I multiply by itself so that it gives me 16? "

We can approach the solution in two ways. The first method is guessing the answer and using trial and error. The second method - more neat - is to use mathematics.

Taking the square root of both sides gives

`\sqrt[]{a^2}=\sqrt[]{16}`

The LHS gives a (since the square root of a square is just the number ); therefore, we have

`a=\sqrt[]{16}`

Since,

`\sqrt[]{16}=+4\text{ or -4}`
`\begin{gathered} a=+4,\text{ or} \\ a=-4 \end{gathered}`

Hence, the correct answer choice is d. -4