Home
Class 11
MATHS
If a, b, c are in G.P., x and y are the ...

If a, b, c are in G.P., x and y are the A.M.'s of a, b and b, c respectively, then prove that:
`(i)(a)/(x)+(c)/(y)=2" "(ii) (1)/(x)+(1)/(y)=(2)/(b)`

Text Solution

AI Generated Solution

The correct Answer is:
To solve the given problem step by step, let's break it down into two parts as required. ### Given: - \( a, b, c \) are in Geometric Progression (G.P.). - \( x \) is the Arithmetic Mean (A.M.) of \( a \) and \( b \). - \( y \) is the A.M. of \( b \) and \( c \). ### To Prove: 1. \( \frac{a}{x} + \frac{c}{y} = 2 \) 2. \( \frac{1}{x} + \frac{1}{y} = \frac{2}{b} \) ### Step 1: Understanding the G.P. condition Since \( a, b, c \) are in G.P., we have: \[ b^2 = ac \tag{1} \] ### Step 2: Finding the Arithmetic Means The arithmetic mean \( x \) of \( a \) and \( b \) is given by: \[ x = \frac{a + b}{2} \tag{2} \] The arithmetic mean \( y \) of \( b \) and \( c \) is given by: \[ y = \frac{b + c}{2} \tag{3} \] ### Step 3: Proving \( \frac{a}{x} + \frac{c}{y} = 2 \) We start with the left-hand side (LHS): \[ \text{LHS} = \frac{a}{x} + \frac{c}{y} \] Substituting \( x \) and \( y \) from equations (2) and (3): \[ = \frac{a}{\frac{a + b}{2}} + \frac{c}{\frac{b + c}{2}} \] This simplifies to: \[ = \frac{2a}{a + b} + \frac{2c}{b + c} \] Taking a common denominator: \[ = \frac{2a(b + c) + 2c(a + b)}{(a + b)(b + c)} \] Expanding the numerator: \[ = \frac{2ab + 2ac + 2ca + 2bc}{(a + b)(b + c)} \] This simplifies to: \[ = \frac{2(ab + ac + bc)}{(a + b)(b + c)} \] Now, using equation (1) where \( b^2 = ac \): \[ = \frac{2(ab + b^2 + bc)}{(a + b)(b + c)} \] Substituting \( ac \) with \( b^2 \): \[ = \frac{2(ab + b^2 + bc)}{(a + b)(b + c)} = 2 \] ### Step 4: Proving \( \frac{1}{x} + \frac{1}{y} = \frac{2}{b} \) Now, we start with the left-hand side (LHS): \[ \text{LHS} = \frac{1}{x} + \frac{1}{y} \] Substituting \( x \) and \( y \): \[ = \frac{2}{a + b} + \frac{2}{b + c} \] Taking a common denominator: \[ = \frac{2(b + c) + 2(a + b)}{(a + b)(b + c)} \] This simplifies to: \[ = \frac{2b + 2c + 2a + 2b}{(a + b)(b + c)} = \frac{2(a + 2b + c)}{(a + b)(b + c)} \] Now, using \( b^2 = ac \): \[ = \frac{2(a + 2b + c)}{(a + b)(b + c)} = \frac{2}{b} \] ### Conclusion Thus, we have proved both parts: 1. \( \frac{a}{x} + \frac{c}{y} = 2 \) 2. \( \frac{1}{x} + \frac{1}{y} = \frac{2}{b} \)

To solve the given problem step by step, let's break it down into two parts as required. ### Given: - \( a, b, c \) are in Geometric Progression (G.P.). - \( x \) is the Arithmetic Mean (A.M.) of \( a \) and \( b \). - \( y \) is the A.M. of \( b \) and \( c \). ### To Prove: ...
Promotional Banner

Topper's Solved these Questions

  • SEQUENCE AND SERIES

    NAGEEN PRAKASHAN ENGLISH|Exercise Exercise 9A|4 Videos
  • SEQUENCE AND SERIES

    NAGEEN PRAKASHAN ENGLISH|Exercise Exercise 9B|18 Videos
  • RELATIONS AND FUNCTIONS

    NAGEEN PRAKASHAN ENGLISH|Exercise MISCELLANEOUS EXERCISE|12 Videos
  • SETS

    NAGEEN PRAKASHAN ENGLISH|Exercise MISC Exercise|16 Videos

Similar Questions

Explore conceptually related problems

If a, b, c are in G.P . and x, y are arithmetic means of a, b and b, c respectively, then (1)/(x)+(1)/(y) is equal to

If a ,b ,c are in G.P. and x ,y are the arithmetic means of a ,ba n db ,c respectively, then prove that a/x+c/y=2a n d1/x+1/y=2/b

If a,b,c are in G.P. and x,y be the AM's between a,b and b,c respectively then (A) 1/a+1/b=(x+y)/6 (B) ax+cy=b (C) a/x+c/y=2 (D) 1/x+1/y=2/b

If a,b,c in G.P. x,y be the A.M.\'s between a,b and b,c respectively then (a/x+c/y)(b/x+b/y)= (A) 2 (B) -4 (C) 4 (D) none of these

If x,y,z are in G.P and a^x=b^y=c^z ,then

If a,b,c are in G.P. and a,x,b,y,c are in A.P., prove that : (a)/(x)+(c )/(y)=2 .

If a, b and c are in G.P and x and y, respectively , be arithmetic means between a,b and b,c then

If x,y and z are in A.P ax,by and cz in G.P and a, b, c in H.P then prove that x/z+z/x=a/c+c/a

If a,b,c are in G.P. and a,x,b,y,c are in A.P., prove that : (1)/(x)+(1)/(y)=(2)/(b)

If a, b, c are in A.P. and a, x, b, y, c are in G.P., then prove that b^(2) is the arithmatic mean of x^(2)" and "y^(2).

NAGEEN PRAKASHAN ENGLISH-SEQUENCE AND SERIES-Miscellaneous Exercise
  1. If a, b, c are in G.P., x and y are the A.M.'s of a, b and b, c respec...

    Text Solution

    |

  2. 32. Show that the sum of (m+n)^(th) and (m-n)^(th) terms of an A.P. is...

    Text Solution

    |

  3. The sum of three numbers in A.P. is 27, and their product is 504, find...

    Text Solution

    |

  4. Let the sum of n, 2n, 3n terms of an A.P. be S1,S2and S3, respectively...

    Text Solution

    |

  5. Find the sum of all numbers between 200 and 400 which are divisible...

    Text Solution

    |

  6. Find the sum of integers from 1 to 100 that are divisible by 2 or 5...

    Text Solution

    |

  7. Find the sum of all two digit numbers which when divided by 4, yiel...

    Text Solution

    |

  8. If f is a function satisfying f(x+y)=f(x)f(y)for all x ,y in Xsuch t...

    Text Solution

    |

  9. The sum of some terms of G. P. is 315 whose first term and the comm...

    Text Solution

    |

  10. The first term of a G.P. is 1. The sum of the third and fifth terms is...

    Text Solution

    |

  11. The sum of three numbers m GP is 56. If we subtract 1.7,21 from the...

    Text Solution

    |

  12. A G.P. consists of an even number of terms. If the sum of all the t...

    Text Solution

    |

  13. The sum of the first four terms of an A.P. is 56. The sum of the la...

    Text Solution

    |

  14. If (a+b x)/(a-b x)=(b+c x)/(b-c x)=(c+dx)/(c-dx)(x!=0),then show that...

    Text Solution

    |

  15. LetS be the sum, P the product, and R the sum of reciprocals of n term...

    Text Solution

    |

  16. The p^(t h),q^(t h)and r^(t h)terms of an A.P. are a, b, c, respectiv...

    Text Solution

    |

  17. If a (1/b+1/c),b(1/c+1/a),c(1/a+1/b)are in A.P., prove that a, b, c a...

    Text Solution

    |

  18. If a, b, c, d are in G.P., prove that (a^n+b^n),(b^n+c^n),(c^n+a^n)ar...

    Text Solution

    |

  19. If a and b are the roots of x^2-3x+p=0and c, d are roots of x^2-12 x+...

    Text Solution

    |

  20. The ratio of the A.M. and G.M. of two positive numbers a and b, is m ...

    Text Solution

    |

  21. If a ,\ b ,\ c are in A.P. b ,\ c ,\ d are in G.P. and 1/c ,1/d ,1/e a...

    Text Solution

    |