Multiple choice general knowledge math & puzzles

Expansion of 1/(1-x) where x<1 is

  1. 1-(x^2)/2!+(x^4)/4!+...

  2. x-(x^3)/3!+(x^5)/5!-...

  3. 1+x+(x^2)/2!+....

  4. 1+x+(x^2)+...
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The binomial expansion of (1-x)^(-1) gives the infinite geometric series 1 + x + x² + x³ + ... for |x| < 1. Option D correctly shows this pattern without factorials in denominators. Options A and B show trigonometric series (cosine and sine respectively) with factorial denominators, while option C incorrectly includes a factorial denominator in the x² term.

Keep practicing — related questions