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Let

f(x)={∣x∣+3if x≤−3−2xif −3<x<36x+2if x≥3f(x)=\begin{cases} |x|+3 & \text{if } x\le -3 \\ -2x & \text{if } -3<x<3 \\ 6x+2 & \text{if } x\ge 3 \end{cases}

Then, which of the following is true?

Solution

✅ Correct Option: 4

A function is continuous at a point if the left-hand limit, right-hand limit, and the actual function value are all equal.

The piecewise function has potential discontinuities at x=−3x = -3 and x=3x = 3.


At x=−3x = -3, using the condition x≤−3x \leq -3:

f(−3)=∣−3∣+3f(-3) = |-3| + 3

f(−3)=3+3f(-3) = 3 + 3

f(−3)=6f(-3) = 6

For the left-hand limit (when x<−3x < -3), using f(x)=∣x∣+3f(x) = |x| + 3:

lim⁡x→−3−f(x)=∣−3∣+3=6\lim_{x \to -3^-} f(x) = |-3| + 3 = 6

For the right-hand limit (when −3<x<3-3 < x < 3), using f(x)=−2xf(x) = -2x:

lim⁡x→−3+f(x)=−2(−3)=6\lim_{x \to -3^+} f(x) = -2(-3) = 6

Since f(−3)=6f(-3) = 6, left limit =6= 6, and right limit =6= 6, the function is continuous at x=−3x = -3.


At x=3x = 3, using the condition x≥3x \geq 3:

f(3)=6(3)+2f(3) = 6(3) + 2

f(3)=18+2f(3) = 18 + 2

f(3)=20f(3) = 20

For the left-hand limit (when −3<x<3-3 < x < 3), using f(x)=−2xf(x) = -2x:

lim⁡x→3−f(x)=−2(3)=−6\lim_{x \to 3^-} f(x) = -2(3) = -6

For the right-hand limit (when x≥3x \geq 3), using f(x)=6x+2f(x) = 6x + 2:

lim⁡x→3+f(x)=6(3)+2=20\lim_{x \to 3^+} f(x) = 6(3) + 2 = 20

Since left limit =−6= -6 and right limit =20= 20, the limits are not equal. The function is discontinuous at x=3x = 3.


The function is continuous at x=−3x = -3 and discontinuous at x=3x = 3.

Therefore, f(x)f(x) is discontinuous at x=3x = 3.

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