1. Choice (b) is correct. The equation of any line parallel to the x-axis is y = k If it passes through the point (2, -3), then its coordinates must satisfy its equation -3 = k Putting the value of k, the equation of the required line is y = -3 This question related to Chapter 9 maths Class 11th NCERT.Read more

    Choice (b) is correct.
    The equation of any line parallel to the x-axis is y = k
    If it passes through the point (2, -3), then its coordinates must satisfy its equation -3 = k
    Putting the value of k, the equation of the required line is y = -3
    This question related to Chapter 9 maths Class 11th NCERT. From the Chapter 9: Straight Lines. Give answer according to your understanding.

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  2. Choice (b) is correct.  We know that in case of distinct numbers A.M. > G.M x + y /2 > √xy, y + z/2 >√yz and z + x /2 >√zx Multiplying above three inequalities, we get  x + y/2 . y + z /2 . z + x /2 >√xy. √yz. √zx  ⇒ (x + y) (y + z) (z + x) >8xyz For more please visit here: https:/Read more

    Choice (b) is correct. 
    We know that in case of distinct numbers A.M. > G.M
    x + y /2 > √xy, y + z/2 >√yz and z + x /2 >√zx
    Multiplying above three inequalities, we get 
    x + y/2 . y + z /2 . z + x /2 >√xy. √yz. √zx 
    ⇒ (x + y) (y + z) (z + x) >8xyz

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    • 3
  3. Choice (c) is correct.  Since x, 2y, 3z are in A.P. 2y = x + 3z/ 2⇒ 4y = x + 3z Again, x, y, z are in G.P. Let r be its common ratio. y = xr and z = yr = (xr)r = xr² Putting values of y and z from (2) in (1), we get  4xr = x +3xr² ⇒ 3r² - 4r + 1 = 0  ⇒  3r² - 3r - r + 1= 0  ⇒ 3r(r - 1) - (r - 1) = 0Read more

    Choice (c) is correct. 
    Since x, 2y, 3z are in A.P.
    2y = x + 3z/ 2⇒ 4y = x + 3z
    Again, x, y, z are in G.P.
    Let r be its common ratio.
    y = xr and z = yr = (xr)r = xr²
    Putting values of y and z from (2) in (1), we get 
    4xr = x +3xr² ⇒ 3r² – 4r + 1 = 0  ⇒  3r² – 3r – r + 1= 0 
    ⇒ 3r(r – 1) – (r – 1) = 0 ⇒ (r – 1)(3r – 1) = 0 ⇒ r = 1 or r = 1/3
    r = 1/3

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    • 12
  4. Choice (d) is correct. Let a and r be the first term and the common ratio of the G.P. Given, any term of the G.P. is equal to the sum of the next two terms.  Tₙ = Tₙ ₊ ₁ + Tₙ ₊ ₂ ⇒ arⁿ ⁻ ¹ = arⁿ + arⁿ ⁺ ¹ ⇒ 1 = r + r² ⇒ r² + r - 1 = 0 ⇒ r = -1 ±√ 1² - 4 × 1 × (-1)/ 2 × 1 = -1 ± √5/2 ⇒ r =√5 - 1/2 ⇒ Read more

    Choice (d) is correct.
    Let a and r be the first term and the common ratio of the G.P.
    Given, any term of the G.P. is equal to the sum of the next two terms. 
    Tₙ = Tₙ ₊ ₁ + Tₙ ₊ ₂ ⇒ arⁿ ⁻ ¹ = arⁿ + arⁿ ⁺ ¹ ⇒ 1 = r + r²
    ⇒ r² + r – 1 = 0
    ⇒ r = -1 ±√ 1² – 4 × 1 × (-1)/ 2 × 1 = -1 ± √5/2
    ⇒ r =√5 – 1/2
    ⇒ r = 2( √5 – 1/2) = 2 sin 18°

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    • 5
  5. Choice (a) is correct. The series is a G.P. with a = 8, r = 1/2, l = 1/128 The nth term lₙ from end is given by lₙ = 1/rⁿ ⁻ ¹  The fourth term l₄ from end is given by l₄ = 1/28/(1/2)³ = 8/128 = 1/16 For more please visit here: https://www.tiwariacademy.com/ncert-solutions/class-11/maths/#chapter-8

    Choice (a) is correct.
    The series is a G.P. with a = 8, r = 1/2, l = 1/128
    The nth term lₙ from end is given by lₙ = 1/rⁿ ⁻ ¹ 
    The fourth term l₄ from end is given by l₄ = 1/28/(1/2)³ = 8/128 = 1/16

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    • 12