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Continuity & Differentiability · Question 28 of 125

Question 28

HardOriginal question

For f(x)=[x]2−[x2]f(x) = [x]^{2} - [x^{2}], what is the left-hand limit at x=2x = 2?

Options for question 28

Show the answer and explanation
CorrectNot quiteAnswer B

Correct answer: B

Explanation

  1. Just left of 2: [x]=1[x] = 1, so [x]2=1[x]^{2} = 1; and x2x^{2} is just below 4, so [x2]=3[x^{2}] = 3.

  2. The left-hand limit is 1−3=−21 - 3 = -2.

Worth noting

0 is f(2)=4−4f(2) = 4 - 4; just below 2 both brackets drop, [x][x] to 1 and [x2][x^{2}] to 3.

Concept
A one-sided limit
Typical time
120 s
Your time
—
The rule this testsContinuity at a point
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Ten questions from Continuity & Differentiability, at your own pace.

Practise this chapter →

Ten questions from Continuity & Differentiability, at your own pace.