Math Problem Statement

Determine the values of a and b so that the following function is continuous for all values of x: f(x) = { 2 for x ≤ -1, ax + b for -1 < x < 3, -2 for x ≥ 3 }

Solution

To determine the values of aa and bb that make the function continuous for all values of xx, we need to ensure that the function is continuous at the points where the piecewise function changes its form. These points are x=1x = -1 and x=3x = 3.

Step 1: Continuity at x=1x = -1

At x=1x = -1, the function transitions from f(x)=2f(x) = 2 to f(x)=ax+bf(x) = ax + b. For continuity at x=1x = -1, the value of the function at x=1x = -1 must be the same from both pieces. So we set:

f(x)=2atx=1f(x) = 2 \quad \text{at} \quad x = -1 and f(x)=ax+batx=1f(x) = ax + b \quad \text{at} \quad x = -1

Substituting x=1x = -1 into the second piece: 2=a(1)+ba+b=2(Equation 1)2 = a(-1) + b \quad \Rightarrow \quad -a + b = 2 \quad \text{(Equation 1)}

Step 2: Continuity at x=3x = 3

At x=3x = 3, the function transitions from f(x)=ax+bf(x) = ax + b to f(x)=2f(x) = -2. For continuity at x=3x = 3, the value of the function at x=3x = 3 must be the same from both pieces. So we set:

f(x)=2atx=3f(x) = -2 \quad \text{at} \quad x = 3 and f(x)=ax+batx=3f(x) = ax + b \quad \text{at} \quad x = 3

Substituting x=3x = 3 into the second piece: 2=a(3)+b3a+b=2(Equation 2)-2 = a(3) + b \quad \Rightarrow \quad 3a + b = -2 \quad \text{(Equation 2)}

Step 3: Solving the System of Equations

Now, we solve the system of two equations:

  1. a+b=2-a + b = 2
  2. 3a+b=23a + b = -2

By subtracting Equation 1 from Equation 2, we eliminate bb: (3a+b)(a+b)=22(3a + b) - (-a + b) = -2 - 2 3a+b+ab=43a + b + a - b = -4 4a=4a=14a = -4 \quad \Rightarrow \quad a = -1

Substitute a=1a = -1 into Equation 1: a+b=2(1)+b=21+b=2b=1-a + b = 2 \quad \Rightarrow \quad -(-1) + b = 2 \quad \Rightarrow \quad 1 + b = 2 \quad \Rightarrow \quad b = 1

Final Answer:

The values of aa and bb that make the function continuous for all values of xx are: a=1andb=1a = -1 \quad \text{and} \quad b = 1

Would you like to explore the next problem or need further clarification on this one?

Here are some related questions:

  1. How do we check if a piecewise function is differentiable?
  2. What does it mean for a function to be continuous at a point?
  3. How can we solve for constants in other piecewise function problems?
  4. What is the concept of left-hand and right-hand limits in continuity?
  5. How do we handle piecewise functions with more than two pieces?

Tip: Always check both the left-hand and right-hand limits when solving for continuity at a point!

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Math Problem Analysis

Mathematical Concepts

Piecewise Functions
Continuity
Algebra

Formulas

f(x) = ax + b
Continuity Condition: lim x→c- f(x) = lim x→c+ f(x)

Theorems

Continuity at a Point
Piecewise Function Continuity

Suitable Grade Level

Grades 11-12