Q. Determine whether the function f(x) is continuous at x=−4.f(x)={1+x2,7+2x,x≥4x<4f(x) is discontinuous at x=−4f(x) is continuous at x=−4
Definition of Continuity: Understand the definition of continuity at a point.A function f(x) is continuous at a point x=a if the following three conditions are met:1. f(a) is defined.2. The limit of f(x) as x approaches a exists.3. The limit of f(x) as x approaches a is equal to f(a).
Check f(−4) Defined: Check if f(−4) is defined.Since −4 is less than 4, we use the piece of the function defined for x < 4, which is f(x)=7+2x.f(−4)=7+2(−4)=7−8=−1.f(−4) is defined and equals −1.
Left Limit at −4: Check the limit of f(x) as x approaches −4 from the left.Since we are approaching −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+2x.limx→−4−f(x)=limx→−4−(7+2x)=7+2(−4)=−1.The limit from the left exists and equals −1.
Right Limit at −4: Check the limit of f(x) as x approaches −4 from the right.Since we are approaching −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+2x.limx→−4+f(x)=limx→−4+(7+2x)=7+2(−4)=−1.The limit from the right exists and equals −1.
Compare Left and Right Limits: Determine if the left-hand limit and right-hand limit are equal.From Steps 3 and 4, we have:limx→−4−f(x)=−1limx→−4+f(x)=−1Since both limits are equal, the limit of f(x) as x approaches −4 exists and equals −1.
Comparison of f(−4) and Limit: Compare the value of f(−4) with the limit of f(x) as x approaches −4. From Step 2, we have f(−4)=−1. From Step 5, we have limx→−4f(x)=−1. Since f(−4) is equal to the limit of f(x) as x approaches −4, the function f(x) is continuous at f(−4)2.
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