Question

this question is from ch-7 maths class 11 if anyone know the answer write it down otherwise get out of here​

Answer 1

${\huge{\underline{\small{\mathbb{\pink{♡Ans:-}}}}}}$

14

explanation :

Let P(15,n−1):P(16,n−2)=3:4P(15,n-1):P(16,n-2)=3:4

⇒.15Pn−1.16Pn−2=34⇒.15Pn-1.16Pn-2=34

⇒15!(15−n+1)!×(16−n+2)!16!=34⇒15!(15-n+1)!×(16-n+2)!16!=34

⇒15!(16−n)!×(18−n)!16!=34⇒15!(16-n)!×(18-n)!16!=34

⇒(18−n)!16(16−n)!=34⇒(18-n)!16(16-n)!=34

⇒(18−n)(17−n)(16−n)!16(16−n)!=34⇒(18-n)(17-n)(16-n)!16(16-n)!=34

⇒(18−n)(17−n)=12⇒(18-n)(17-n)=12

⇒306−17n−18n+n2=12⇒306-17n-18n+n2=12

⇒n2−35n+294=0⇒n2-35n+294=0

⇒(n−14)(n−21)=0⇒(n-14)(n-21)=0

⇒n=14 (∵n≠21)⇒n=14 (∵n≠21)

Answer 2

Answer:

14

explanation :

Let P(15,n−1):P(16,n−2)=3:4P(15,n-1):P(16,n-2)=3:4

⇒.15Pn−1.16Pn−2=34⇒.15Pn-1.16Pn-2=34

⇒15!(15−n+1)!×(16−n+2)!16!=34⇒15!(15-n+1)!×(16-n+2)!16!=34

⇒15!(16−n)!×(18−n)!16!=34⇒15!(16-n)!×(18-n)!16!=34

⇒(18−n)!16(16−n)!=34⇒(18-n)!16(16-n)!=34

⇒(18−n)(17−n)(16−n)!16(16−n)!=34⇒(18-n)(17-n)(16-n)!16(16-n)!=34

⇒(18−n)(17−n)=12⇒(18-n)(17-n)=12

⇒306−17n−18n+n2=12⇒306-17n-18n+n2=12

⇒n2−35n+294=0⇒n2-35n+294=0

⇒(n−14)(n−21)=0⇒(n-14)(n-21)=0

⇒n=14 (∵n≠21)⇒n=14 (∵n≠21)

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Step-by-step explanation:

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