Math Problem Statement

Is f(x) continue dans R

Is f(x) continue dans R

Solution

To check whether the function f(x)f(x) is continuous on R\mathbb{R}, we need to verify the following:

  1. Continuity at all points where x0x \geq 0: This would involve analyzing the function 3xx2x+1\frac{3\sqrt{x}}{x^2 - x + 1} for x0x \geq 0.

  2. Continuity at all points where x<0x < 0: We need to check the continuity of x2sin(x2)x^2 \sin(x - 2) for x<0x < 0.

  3. Continuity at the point x=0x = 0, where the two parts of the piecewise function meet.

Step-by-step analysis:

1. Continuity for x0x \geq 0:

The first part of the function is f(x)=3xx2x+1f(x) = \frac{3\sqrt{x}}{x^2 - x + 1} for x0x \geq 0.

  • For x0x \geq 0, both the numerator 3x3\sqrt{x} and the denominator x2x+1x^2 - x + 1 are continuous functions.
  • The denominator x2x+1x^2 - x + 1 does not vanish for any real xx, ensuring there are no singularities in this part of the function.

Thus, f(x)f(x) is continuous for x0x \geq 0.

2. Continuity for x<0x < 0:

The second part of the function is f(x)=x2sin(x2)f(x) = x^2 \sin(x - 2) for x<0x < 0.

  • This is the product of a continuous function x2x^2 and a continuous trigonometric function sin(x2)\sin(x - 2).
  • Therefore, this part is continuous for all x<0x < 0.

3. Continuity at x=0x = 0:

To check the continuity at x=0x = 0, we need to confirm that: limx0f(x)=limx0+f(x)=f(0)\lim_{x \to 0^-} f(x) = \lim_{x \to 0^+} f(x) = f(0)

For x0+x \to 0^+:

limx0+3xx2x+1=30020+1=0\lim_{x \to 0^+} \frac{3\sqrt{x}}{x^2 - x + 1} = \frac{3\sqrt{0}}{0^2 - 0 + 1} = 0

For x0x \to 0^-:

limx0x2sin(x2)=02sin(02)=0\lim_{x \to 0^-} x^2 \sin(x - 2) = 0^2 \cdot \sin(0 - 2) = 0

Both limits are equal to 0, and the value of the function at x=0x = 0 (from either side) is also 0. Thus, f(0)=0f(0) = 0.

Conclusion:

Since the function is continuous on both intervals and the left-hand and right-hand limits at x=0x = 0 are equal, f(x)f(x) is continuous on R\mathbb{R}.

Would you like more details or have any questions?


Here are 5 related questions you might find helpful:

  1. How do you check differentiability for piecewise functions like this one?
  2. What are some examples of functions that are continuous but not differentiable?
  3. How do we ensure a function is smooth (continuously differentiable)?
  4. Can this function be integrated over all real numbers, and how do we evaluate that?
  5. How do you handle discontinuities or singularities in a function?

Tip: When evaluating continuity at a point, always compare the left-hand and right-hand limits, as well as the function's value at that point.

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Math Problem Analysis

Mathematical Concepts

Continuity
Piecewise Functions
Limits

Formulas

f(x) = 3√x / (x^2 - x + 1) for x ≥ 0
f(x) = x^2 sin(x - 2) for x < 0
lim x→0^- f(x)
lim x→0^+ f(x)

Theorems

Limit Definition of Continuity
Squeeze Theorem

Suitable Grade Level

Undergraduate Math