Simple but confusing

Calculus Level 2

Which of the following is/are true?

(A) ∞ = ∞ (B) 1/∞ =1/∞ (C) +∞ > -∞ (D) ∞/∞ = ∞/∞

A only A and B only A and D only B only C only B and C only None of them D only

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1 solution

Nanda Rahsyad
Dec 13, 2015

Infinity is a number that's expressed as x 0 \frac{x}{0} with x being all possible numbers. The equation itself is wrong, so none of those statements are correct.

But +∞ should be greater than -∞ as +∞ lies on right side and -∞ lies on the left side of origin on the number line, right? Whenever one represents range of a function, say y=x^3, range is represented as y belongs to (-∞,∞). Since while representing range, one writes lowest value first, then highest value achieved by that function, separated by a comma, enclosed in brackets, this should imply -∞ should be less than+∞. Please clear my doubt.

Swapnil Roge - 5 years, 6 months ago

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statement: = + 1 = + 2 = . . = + 2 -\infty=-\infty+1=-\infty+2=..=-\infty+2\infty

now we cannot determine + 2 -\infty+2\infty . but i think you get the idea right. you can never do arithmetic with infinity. remember this. you can do if limit is given or it is the upper/lower bound of a sum, improper integral,product etc. hope this helps

Aareyan Manzoor - 5 years, 6 months ago

while you are right, the defination of infinity is not x 0 \frac{x}{0} . x 0 \frac{x}{0} cannot be defined. l i m n 0 + x n lim_{n\rightarrow 0^+} \frac{x}{n} , is infinity. what you did is the same as 1 = 0 \frac{1}{\infty}=0 . please correct the solution.

Aareyan Manzoor - 5 years, 6 months ago

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