# permutations and combinations

the number of arrangements of the word "DELHI" in which E precedes I is

Note by Rama Rao
4 years, 7 months ago

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There are $$5!$$ ways to arrange the letters. Each permutation where E comes before I has a pair where E comes after I (namely swap E and I), so the number of permutations where E comes before I is exactly half of it, or $$5!/2 = 60$$.

- 4 years, 7 months ago

If f is a differentiable function and f(x^2-y^2 )=xf(x)-yf(y)  and f(1)=2,then find f(2).


- 4 years, 5 months ago

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- 4 years, 2 months ago