Mathematics
Grade 11
15 min
Evaluate exponential functions
Evaluate exponential functions
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Introduction & Learning Objectives
Learning Objectives
Evaluate an exponential function for a given integer value.
Evaluate an exponential function for a given rational (fractional) value without a calculator.
Use a calculator to approximate the value of an exponential function for an irrational input.
Evaluate the natural exponential function, f(x) = e^x, for various inputs using a calculator.
Substitute a given value into an exponential model to determine an output in a real-world context.
Correctly apply the order of operations when evaluating exponential functions of the form f(x) = ab^x.
Ever wonder how a single social media post can go viral, reaching millions of people in just a few hours? 📈 That's the power of exponential growth!
In this tutorial, you will learn the fundamental skill of evaluat...
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Key Concepts & Vocabulary
TermDefinitionExample
Exponential FunctionA function of the form f(x) = ab^x, where 'a' is the non-zero initial value, 'b' is the base (b > 0 and b ≠1), and 'x' is the exponent.f(x) = 3(2)^x is an exponential function with an initial value of 3 and a base of 2.
Base (b)The constant value that is raised to the power of the variable exponent. It determines the rate of growth (if b > 1) or decay (if 0 < b < 1).In the function g(t) = 10(0.5)^t, the base is 0.5, indicating exponential decay.
Initial Value (a)The output of the function when the input (x) is zero. It represents the starting amount in many real-world models.For P(t) = 500(1.05)^t, the initial value is 500. This could represent an initial investment of $500.
Rational ExponentAn exponent t...
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Core Formulas
The General Exponential Function Form
f(x) = ab^x
To evaluate, substitute the given value for 'x' into the exponent. Always calculate the power (b^x) first before multiplying by the coefficient 'a', following the order of operations (PEMDAS/BODMAS).
Rational Exponent Rule
b^{m/n} = (\sqrt[n]{b})^m = \sqrt[n]{b^m}
Use this rule to evaluate exponential functions for fractional inputs. It's often easier to take the n-th root of the base 'b' first, then raise the result to the m-th power.
Negative Exponent Rule
b^{-x} = \frac{1}{b^x}
If the exponent is negative, take the reciprocal of the base raised to the positive exponent. This is a key prerequisite for evaluating functions at negative inputs.
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Challenging
Given f(x) = 2(16)^x, find the value of the expression f(3/4) / f(1/2).
A.2
B.4
C.1/2
D.1
Challenging
The population of a town is modeled by P(t) = 10000(1.02)^t and the number of houses is H(t) = 4000(1.01)^t. What is the approximate number of people per house after 10 years? (Round to two decimal places)
A.2.50
B.2.76
C.2.21
D.3.01
Challenging
Using a calculator, approximate the value of f(√2) for the function f(x) = 5(3)^x. Round your answer to the nearest hundredth.
A.21.22
B.15.00
C.23.59
D.9.74
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