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Determine whether the function 
f(x) is continuous at 
x=-4.

f(x)={[1+x^(2)",",x >= 4],[7+2x",",x < 4]:}

f(x) is discontinuous at 
x=-4

f(x) is continuous at 
x=-4

Determine whether the function f(x) f(x) is continuous at x=4 x=-4 .\newlinef(x)={1+x2,amp;x47+2x,amp;xlt;4 f(x)=\left\{\begin{array}{ll} 1+x^{2}, &amp; x \geq 4 \\ 7+2 x, &amp; x&lt;4 \end{array}\right. \newlinef(x) f(x) is discontinuous at x=4 x=-4 \newlinef(x) f(x) is continuous at x=4 x=-4

Full solution

Q. Determine whether the function f(x) f(x) is continuous at x=4 x=-4 .\newlinef(x)={1+x2,x47+2x,x<4 f(x)=\left\{\begin{array}{ll} 1+x^{2}, & x \geq 4 \\ 7+2 x, & x<4 \end{array}\right. \newlinef(x) f(x) is discontinuous at x=4 x=-4 \newlinef(x) f(x) is continuous at x=4 x=-4
  1. Definition of Continuity: Understand the definition of continuity at a point.\newlineA function f(x)f(x) is continuous at a point x=ax=a if the following three conditions are met:\newline11. f(a)f(a) is defined.\newline22. The limit of f(x)f(x) as xx approaches aa exists.\newline33. The limit of f(x)f(x) as xx approaches aa is equal to f(a)f(a).
  2. Check f(4)f(-4) Defined: Check if f(4)f(-4) is defined.\newlineSince 4-4 is less than 44, we use the piece of the function defined for x < 4, which is f(x)=7+2xf(x) = 7 + 2x.\newlinef(4)=7+2(4)=78=1f(-4) = 7 + 2(-4) = 7 - 8 = -1.\newlinef(4)f(-4) is defined and equals 1-1.
  3. Left Limit at 4-4: Check the limit of f(x)f(x) as xx approaches 4-4 from the left.\newlineSince we are approaching 4-4 from the left, we are still in the region where x < 4, so we use the same piece of the function, f(x)=7+2xf(x) = 7 + 2x.\newlinelimx4f(x)=limx4(7+2x)=7+2(4)=1\lim_{x \to -4^-} f(x) = \lim_{x \to -4^-} (7 + 2x) = 7 + 2(-4) = -1.\newlineThe limit from the left exists and equals 1-1.
  4. Right Limit at 4-4: Check the limit of f(x)f(x) as xx approaches 4-4 from the right.\newlineSince we are approaching 4-4 from the right, we are still in the region where x < 4, so we use the same piece of the function, f(x)=7+2xf(x) = 7 + 2x.\newlinelimx4+f(x)=limx4+(7+2x)=7+2(4)=1\lim_{x \to -4^+} f(x) = \lim_{x \to -4^+} (7 + 2x) = 7 + 2(-4) = -1.\newlineThe limit from the right exists and equals 1-1.
  5. Compare Left and Right Limits: Determine if the left-hand limit and right-hand limit are equal.\newlineFrom Steps 33 and 44, we have:\newlinelimx4f(x)=1\lim_{x \to -4^-} f(x) = -1\newlinelimx4+f(x)=1\lim_{x \to -4^+} f(x) = -1\newlineSince both limits are equal, the limit of f(x)f(x) as xx approaches 4-4 exists and equals 1-1.
  6. Comparison of f(4)f(-4) and Limit: Compare the value of f(4)f(-4) with the limit of f(x)f(x) as xx approaches 4-4. From Step 22, we have f(4)=1f(-4) = -1. From Step 55, we have limx4f(x)=1\lim_{x \to -4} f(x) = -1. Since f(4)f(-4) is equal to the limit of f(x)f(x) as xx approaches 4-4, the function f(x)f(x) is continuous at f(4)f(-4)22.

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