Question

Specify whether the given function is even, odd, or neither, and then sketch its graph. $$ h(x)=\left\\{\begin{array}{ll} -x^{2}+4 & \text { if } x \leq 1 \\ 3 x & \text { if } x>1 \end{array}\right. $$

Short answer

The function is neither even nor odd; it shows different symmetry in its defined segments.

Step-by-step solution

Understand Even and Odd Functions

An even function satisfies the condition \( f(-x) = f(x) \) for all \( x \) in the domain, which means it is symmetric about the y-axis. An odd function satisfies the condition \( f(-x) = -f(x) \) for all \( x \) in the domain, indicating symmetry about the origin. If neither condition is met, the function is neither even nor odd.

Check Even/Odd Condition for \( x \leq 1 \)

For \( h(x) = -x^2 + 4 \), test for evenness: \( h(-x) = -(-x)^2 + 4 = -x^2 + 4 = h(x) \). This part is even. Test for oddness: \( h(-x) = h(x) eq -h(x) \), hence not odd.

Check Even/Odd Condition for \( x > 1 \)

For \( h(x) = 3x \), test for evenness: \( h(-x) = 3(-x) = -3x eq 3x = h(x) \), hence this part is not even. Test for oddness: \( h(-x) = -3x = -h(x) \), hence this part is odd.

Determine if Entire Function is Even, Odd, or Neither

Since the function is even for \( x \leq 1 \) and odd for \( x > 1 \), the function as a whole cannot be classified as solely even or odd. Therefore, the function is neither even nor odd.

Sketch the Graph

Plot the function on a coordinate graph: - For \( x \leq 1 \), sketch \( y = -x^2 + 4 \), which is a downward-opening parabola, ending at the point (1, 3). - For \( x > 1 \), sketch \( y = 3x \), which is a straight line starting from \( (1, 3) \) and increasing linearly.

Key concepts

Even Functions

Even functions have a unique and symmetrical characteristic. Imagine looking at a graph directly from the front and seeing a mirror-like reflection across the y-axis. This is what happens with even functions, as they satisfy the condition \( f(-x) = f(x) \) for every \( x \) in their domain. A classical example is \( f(x) = x^2 \), which exhibits perfect reflection symmetry about the y-axis.

To determine if a function is even, substitute \( -x \) into the function and simplify. If the resulting expression is equal to the original function, you have an even function. In the given exercise, the function \( h(x) = -x^2 + 4 \) for \( x \leq 1 \) shows that it's even. This means if we flip over the x-axis, the curve remains the same.

Even functions highlight balance and symmetry, which makes their graphs particularly satisfying to study.

Odd Functions

Odd functions are a bit like spinning a pinwheel; they exhibit a sort of rotational symmetry about the origin. For a function to be labeled as odd, it must satisfy the condition \( f(-x) = -f(x) \) for every \( x \) in its domain. A classic odd function is \( f(x) = x^3 \), which spins symmetrically around the origin.

Checking for oddness involves substituting \( -x \) into the function and checking if the output is the negative of the function's original output. For the exercise problem, the segment \( h(x) = 3x \) for \( x > 1 \) is odd because flipping \( x \) results in a negative output, fulfilling \( h(-x) = -h(x) \).

Understanding odd functions can be particularly helpful when looking at graphs where rotating 180 degrees around the origin mirrors the original layout.

Function Symmetry

Function symmetry is a fundamental concept that helps us quickly understand the nature of a graph. Symmetry in functions can manifest in different forms, primarily even symmetry (y-axis symmetry) and odd symmetry (origin symmetry). Recognizing these symmetry patterns simplifies graph analysis and sketching.

• Even Symmetry: This occurs when the graph is identical on both sides of the y-axis. Function satisfies \( f(-x) = f(x) \).
• Odd Symmetry: This type of symmetry is present when the graph can be rotated 180 degrees around the origin to appear unchanged. Function satisfies \( f(-x) = -f(x) \).

The original exercise shows that while \( h(x) = -x^2 + 4 \) is even for \( x \leq 1 \), and \( h(x) = 3x \) is odd for \( x > 1 \), the entire function is neither solely even nor odd when considering the entire domain.

Graph Sketching

Graph sketching for piecewise functions combines multiple function sections into one coherent graph. This allows us to visualize the overall behavior of a function and each of its segments separately. When dealing with piecewise functions, the first step is to identify boundary points where the function changes form, such as where \( x = 1 \) in the exercise.

• For \( x \leq 1 \): Sketch \( y = -x^2 + 4 \). This part is a downward-opening parabola. The graph peaks at \( (0, 4) \) and concludes at \( (1, 3) \).
• For \( x > 1 \): Sketch \( y = 3x \). This is a linear segment starting at \( (1, 3) \) and moving upwards with a constant slope of 3.

Place each segment precisely in its respective domain range, ensuring continuity of the function. Graph sketching gives a bird's eye view of both algebraic expressions working together to form a complete picture.