Question and Answers Forum

say you have 3 (different) books about mathematics, 4 (different) books about physics and 5 (different) books about chemistry. in how many ways can you arrange them in a shelf such that no two books from the same subject are adjacent?

$${say}\:{you}\:{have}\:\mathrm{3}\:\left({different}\right)\:{books} \\ $$$${about}\:{mathematics},\:\mathrm{4}\:\left({different}\right) \\ $$$${books}\:{about}\:{physics}\:{and}\:\mathrm{5}\:\left({different}\right) \\ $$$${books}\:{about}\:{chemistry}.\:{in}\:{how}\:{many} \\ $$$${ways}\:{can}\:{you}\:{arrange}\:{them}\:{in}\:{a}\:{shelf} \\ $$$${such}\:{that}\:{no}\:{two}\:{books}\:{from}\:{the}\:{same} \\ $$$${subject}\:{are}\:{adjacent}? \\ $$

Question Number 195964 Answers: 1 Comments: 0

the family A has 5 members and the family B has 4 members. there are 6 personsfrom other families. in how many ways can you arrange these 15 persons around a round table such that no member from family A and no member from family B are next to each other?

$${the}\:{family}\:{A}\:{has}\:\mathrm{5}\:{members}\:{and}\:{the} \\ $$$${family}\:{B}\:{has}\:\mathrm{4}\:{members}.\:{there}\:{are}\: \\ $$$$\mathrm{6}\:{personsfrom}\:{other}\:{families}. \\ $$$${in}\:{how}\:{many}\:{ways}\:{can}\:{you}\:{arrange} \\ $$$${these}\:\mathrm{15}\:{persons}\:{around}\:{a}\:{round}\:{table} \\ $$$${such}\:{that}\:{no}\:{member}\:{from}\:{family}\:{A} \\ $$$${and}\:{no}\:{member}\:{from}\:{family}\:{B}\:{are} \\ $$$${next}\:{to}\:{each}\:{other}? \\ $$

Question Number 195666 Answers: 1 Comments: 2

sequence of string said to be orderly if element index i different to i+1 for example aba has orderly value 2 abab has orderly value 3 abaabb has orderly value 3 if there are 7 a and 13 b example aaaaaaabbbbbbbbbbbbb has orderly value 1 what is the mean of its orderly value for all possible sequences?

$$ \\ $$$$\:{sequence}\:{of}\:{string}\:{said}\:{to}\:{be}\:{orderly} \\ $$$$\:{if}\:{element}\:{index}\:{i}\:{different}\:{to}\:{i}+\mathrm{1} \\ $$$$\:{for}\:{example} \\ $$$$\:{aba}\:{has}\:{orderly}\:{value}\:\mathrm{2} \\ $$$$\:{abab}\:{has}\:{orderly}\:{value}\:\mathrm{3} \\ $$$$\:{abaabb}\:{has}\:{orderly}\:{value}\:\mathrm{3} \\ $$$$\:{if}\:{there}\:{are}\:\mathrm{7}\:{a}\:{and}\:\mathrm{13}\:{b} \\ $$$$\:{example} \\ $$$$\:{aaaaaaabbbbbbbbbbbbb}\:{has}\:{orderly}\:{value}\:\mathrm{1} \\ $$$$\:{what}\:{is}\:{the}\:{mean}\:{of}\:{its}\:{orderly}\:{value} \\ $$$$\:{for}\:{all}\:{possible}\:{sequences}? \\ $$$$ \\ $$

Question Number 195672 Answers: 2 Comments: 0

how many different words can be formed from the letters in aaacdefgbbbb such that a “a” and a “b” are not next to each other? (see also Q#195606)

$${how}\:{many}\:{different}\:{words}\:{can}\:{be} \\ $$$${formed}\:{from}\:{the}\:{letters}\:{in} \\ $$$$\boldsymbol{{aaacdefgbbbb}} \\ $$$${such}\:{that}\:{a}\:``\boldsymbol{{a}}''\:{and}\:{a}\:``\boldsymbol{{b}}''\:{are}\:{not} \\ $$$${next}\:{to}\:{each}\:{other}? \\ $$$$ \\ $$$$\left({see}\:{also}\:{Q}#\mathrm{195606}\right) \\ $$

Question Number 195538 Answers: 1 Comments: 7

Number of distributions of n different articles to r different boxes so as 1)empty box allowed 2)empty box not allowed with proof...kindly help me

$${Number}\:{of}\:{distributions}\:{of} \\ $$$${n}\:{different}\:{articles}\:{to}\:{r}\:{different}\:\:{boxes} \\ $$$$\left.{so}\:{as}\:\mathrm{1}\right){empty}\:{box}\:{allowed} \\ $$$$\left.\mathrm{2}\right){empty}\:{box}\:{not}\:{allowed} \\ $$$${with}\:{proof}...{kindly}\:{help}\:{me} \\ $$

Question Number 197578 Answers: 1 Comments: 1

Question Number 195015 Answers: 1 Comments: 0

Question Number 194960 Answers: 1 Comments: 0

Soit x>1. On de^ finie la suite (p_n ) par p_1 =x et ∀n∈IN^∗ p_(n+1) =2p_n ^2 −1 Montrer que lim_(n→+∞) Π_(k=1) ^n (1+(1/p_k ))=(√((x+1)/(x−1)))

$$\mathrm{Soit}\:{x}>\mathrm{1}.\:\mathrm{On}\:\mathrm{d}\acute {\mathrm{e}finie}\:\mathrm{la}\:\mathrm{suite}\:\left(\mathrm{p}_{\mathrm{n}} \right)\:\mathrm{par}\: \\ $$$$\mathrm{p}_{\mathrm{1}} ={x}\:\:\mathrm{et}\:\forall\mathrm{n}\in\mathrm{IN}^{\ast} \:\:\:\:\:\mathrm{p}_{\mathrm{n}+\mathrm{1}} =\mathrm{2p}_{\mathrm{n}} ^{\mathrm{2}} −\mathrm{1} \\ $$$$\mathrm{Montrer}\:\mathrm{que}\:\underset{\mathrm{n}\rightarrow+\infty} {\mathrm{lim}}\:\underset{\mathrm{k}=\mathrm{1}} {\overset{\mathrm{n}} {\prod}}\left(\mathrm{1}+\frac{\mathrm{1}}{\mathrm{p}_{\mathrm{k}} }\right)=\sqrt{\frac{{x}+\mathrm{1}}{{x}−\mathrm{1}}} \\ $$

Question Number 194638 Answers: 1 Comments: 1

Prove that ∀n∈IN^∗ Σ_(k=1) ^(2^n −1) (1/(sin^2 (((kπ)/2^(n+1) ))))= ((2^(2n+1) −2)/3) Give in terms of n Σ_(k=1) ^(2^n −1) (1/(sin^4 (((kπ)/2^(n+1) ))))

$$\mathrm{Prove}\:\mathrm{that}\:\forall{n}\in\mathrm{IN}^{\ast} \:\:\:\:\: \\ $$$$\:\:\:\underset{{k}=\mathrm{1}} {\overset{\mathrm{2}^{{n}} −\mathrm{1}} {\sum}}\:\frac{\mathrm{1}}{{sin}^{\mathrm{2}} \left(\frac{{k}\pi}{\mathrm{2}^{{n}+\mathrm{1}} }\right)}=\:\frac{\mathrm{2}^{\mathrm{2}{n}+\mathrm{1}} −\mathrm{2}}{\mathrm{3}} \\ $$$$\mathrm{Give}\:\mathrm{in}\:\mathrm{terms}\:\mathrm{of}\:{n}\:\:\:\underset{{k}=\mathrm{1}} {\overset{\mathrm{2}^{{n}} −\mathrm{1}} {\sum}}\:\frac{\mathrm{1}}{{sin}^{\mathrm{4}} \left(\frac{{k}\pi}{\mathrm{2}^{{n}+\mathrm{1}} }\right)} \\ $$

Question Number 193864 Answers: 1 Comments: 0

Question Number 193368 Answers: 2 Comments: 0

If log_a y = (1/3) and log_8 a = x + 1 then show that y = 2^(x + 1)

$$\mathrm{If}\:\mathrm{log}_{{a}} {y}\:=\:\frac{\mathrm{1}}{\mathrm{3}}\:\mathrm{and}\:\mathrm{log}_{\mathrm{8}} {a}\:=\:{x}\:+\:\mathrm{1}\:\mathrm{then}\:\mathrm{show} \\ $$$$\mathrm{that}\:{y}\:=\:\mathrm{2}^{{x}\:+\:\mathrm{1}} \\ $$

Question Number 192960 Answers: 0 Comments: 0

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Question Number 192256 Answers: 0 Comments: 0

given f(x)=cx(x−20) and A=(2,5) find the nearst point to A on the graph

$$\mathrm{given}\:{f}\left({x}\right)={cx}\left({x}−\mathrm{20}\right)\:\mathrm{and}\:{A}=\left(\mathrm{2},\mathrm{5}\right) \\ $$$$\mathrm{find}\:\mathrm{the}\:\mathrm{nearst}\:\mathrm{point}\:\mathrm{to}\:{A}\:\mathrm{on}\:\mathrm{the}\:\mathrm{graph} \\ $$

Question Number 191934 Answers: 1 Comments: 0

Question Number 191277 Answers: 0 Comments: 0

Question Number 190738 Answers: 0 Comments: 0

∫_0 ^( (π/2)) (((sin((x/2^n )))/(sinx))) dx , n ∈ N

$$\int_{\mathrm{0}} ^{\:\frac{\pi}{\mathrm{2}}} \:\left(\frac{{sin}\left(\frac{{x}}{\mathrm{2}^{{n}} }\right)}{{sinx}}\right)\:{dx}\:,\:{n}\:\in\:\mathbb{N} \\ $$

Question Number 190602 Answers: 1 Comments: 0

let S={a,b,c,d,e,f} if we take any subset S (same subset is allowed), it also can be S, which will form S if we join them, order of operation does not matter ({a,b,c,d},{d,e,f}) is the same as ({d,e,f},{a,b,c,d}) how many ways can we choose?

$$ \\ $$$$\: \\ $$$$\:{let}\:{S}=\left\{{a},{b},{c},{d},{e},{f}\right\} \\ $$$$\:{if}\:{we}\:{take}\:{any}\:{subset}\:{S}\:\left({same}\:{subset}\:{is}\:{allowed}\right), \\ $$$$\:{it}\:{also}\:{can}\:{be}\:{S},\:{which}\:{will}\:{form}\:{S}\:{if}\:{we}\:{join}\:{them}, \\ $$$${order}\:{of}\:{operation}\:{does}\:{not}\:{matter} \\ $$$$\:\left(\left\{{a},{b},{c},{d}\right\},\left\{{d},{e},{f}\right\}\right)\:{is}\:{the}\:{same}\:{as} \\ $$$$\:\left(\left\{{d},{e},{f}\right\},\left\{{a},{b},{c},{d}\right\}\right) \\ $$$$\:{how}\:{many}\:{ways}\:{can}\:{we}\:{choose}? \\ $$$$\: \\ $$$$ \\ $$

Question Number 190347 Answers: 1 Comments: 0

how is solution lim_(x→sinπ ) ((sin(π/2))/(sinx))=?

$${how}\:{is}\:{solution} \\ $$$$\underset{{x}\rightarrow\mathrm{sin}\pi\:} {\mathrm{lim}}\frac{\mathrm{sin}\frac{\pi}{\mathrm{2}}}{\mathrm{sin}{x}}=? \\ $$

Question Number 190260 Answers: 1 Comments: 0

f : [1, 3] →R , f(x) = (1/x) A(1, 1) B(1, (1/3)) B′(b, (1/b)) , b ≥ 1 Find i. equation of line AB′ ii. equation of tangent T ′ to C_f at point with x = ((1 + b)/2) iii. Study relative positions of L_(AB ′) , T ′ to C_f

$${f}\::\:\left[\mathrm{1},\:\mathrm{3}\right]\:\rightarrow\mathbb{R}\:,\:{f}\left({x}\right)\:=\:\frac{\mathrm{1}}{{x}} \\ $$$${A}\left(\mathrm{1},\:\mathrm{1}\right) \\ $$$${B}\left(\mathrm{1},\:\frac{\mathrm{1}}{\mathrm{3}}\right) \\ $$$${B}'\left({b},\:\frac{\mathrm{1}}{{b}}\right)\:,\:{b}\:\geqslant\:\mathrm{1} \\ $$$${Find} \\ $$$${i}.\:{equation}\:{of}\:{line}\:{AB}' \\ $$$${ii}.\:{equation}\:{of}\:{tangent}\:{T}\:'\:{to}\:{C}_{{f}} \:{at}\:{point} \\ $$$${with}\:{x}\:=\:\frac{\mathrm{1}\:+\:{b}}{\mathrm{2}} \\ $$$${iii}.\:{Study}\:{relative}\:{positions}\:{of}\:{L}_{{AB}\:'} \:,\:{T}\:'\:{to}\:{C}_{{f}} \\ $$

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