137k views
4 votes
If (x, 1/100) lies on the graph of y = 10^x, then x =

2
-1/2
-2

User GoRoS
by
7.6k points

1 Answer

5 votes

TLDR: The answer is -2.

What you have here is a function with a point on the graph. It is understood that “x” represents the input and “y” represents the output, so we’re looking for the right “x” that will give y = 1/100.

To start, we can substitute the y-value into the function like this:

y = 10^x

1/100 = 10^x

From here, we can take two different pathways; one requires conceptual knowledge while the other relies on the knowledge of logarithms.

Conceptual

For the conceptual, we know that 100 = 10^2, so 1/100 is the same as 1/10^2. We also know that the inverse of a fraction is the same as the number to the negative of its power (for example, 1/2 is equal to 2^-1), so we know that 1/10^2 is the same as 10^-2. So far, we have learned that:

1/100 = 10^x

1/10^2 = 10^x

10^-2 = 10^x

So, to satisfy this, “x” must equal -2.

Logarithms

For logarithms, we can use powers and math to actually calculate the value of “x”. We know that:

1/100 = 10^x

To solve this, we need “x” to be by itself on one side of the equation. To do this, we can perform the inverse function of an exponent, which is a logarithm. In this case, the base of 10^x is 10, so we need a “base 10” logarithm to solve this function. Apply this function to both sides and simplify:

1/100 = 10^x

log10(1/100) = log10(10^x)

log10(1/100) = x

The log10 function is the inverse of 10^x, so they cancel out to leave “x”. Plug log10(1/100) into a calculator, and you find that x = -2.

Hope this helps!

User Harneet Kaur
by
8.8k points

No related questions found

Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.

9.4m questions

12.2m answers

Categories