Math Problem Statement

Find the exponential equation whose graph passes through the points (-3,1/2) and (1,8)

Solution

To find the exponential equation of the form:

y=abxy = ab^x

that passes through the points (3,12)(-3, \frac{1}{2}) and (1,8)(1, 8), follow these steps:

Step 1: Plug in the points into the general equation

From (3,12)(-3, \frac{1}{2}): 12=ab3(1)\frac{1}{2} = ab^{-3} \quad \text{(1)}

From (1,8)(1, 8): 8=ab1(2)8 = ab^1 \quad \text{(2)}

Step 2: Solve for aa and bb

Equation (2):

8=ab    a=8b(3)8 = ab \implies a = \frac{8}{b} \quad \text{(3)}

Substitute equation (3) into equation (1):

12=8bb3=8b4\frac{1}{2} = \frac{8}{b}b^{-3} = \frac{8}{b^4}

Multiply both sides by b4b^4:

12b4=8b4=16b=2\frac{1}{2}b^4 = 8 \quad \Rightarrow \quad b^4 = 16 \quad \Rightarrow \quad b = 2

Step 3: Solve for aa

Substitute b=2b = 2 into equation (3):

a=82=4a = \frac{8}{2} = 4

Final Equation

Thus, the exponential equation is:

y=4(2)xy = 4(2)^x

Verification

Let's verify by plugging in the given points:

  • For (3,12)(-3, \frac{1}{2}): y=4(2)3=4×18=48=12y = 4(2)^{-3} = 4 \times \frac{1}{8} = \frac{4}{8} = \frac{1}{2}

  • For (1,8)(1, 8): y=4(2)1=4×2=8y = 4(2)^1 = 4 \times 2 = 8

Both points satisfy the equation.

Would you like more details or have any questions?


Here are 5 related questions to consider:

  1. How can you find an exponential equation with more than two points?
  2. What happens if the base bb is a fraction instead of an integer?
  3. How can you determine if a graph represents an exponential function?
  4. How do transformations affect the graph of an exponential equation?
  5. Can you find an exponential equation passing through negative yy-values?

Tip: When solving exponential equations, solving for the base bb first helps simplify finding the constant aa.

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Math Problem Analysis

Mathematical Concepts

Algebra
Exponential Functions

Formulas

y = ab^x

Theorems

Exponential Equation Solving

Suitable Grade Level

Grades 9-12