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mathcity.org Merging man and maths Exercise 6.3 (Solutions)  Textbook of lgebra and Trigonometry for Class XI Available online @ http://www.mat hcity.org, Version: 1.0.0  Question # 1 (i)  35 and 55 Here 3 5 a =  and 55 b = , so A.M. 35 55 8 5 4 5 2 2 2 a b + + = = = =  (ii)  Same as (i) and (ii) (iii) 2 1  x x +  and 2 1  x x + +  Here 2 1 a x x = +  and 2 1 b x x = + +  A.M. 2 2 2 2 1 1 2 2 1 2 2 2 a b x x x x x  x + + + + + + = = = = +  Question # 2 Since 5, 8 are two A.Ms between a and b. Therefore a, 5, 8, b are in A.P. Here 1 a a =  and d  = 8 – 5 = 3  Now 2 1 a a d = +  5 3 5 3 2 a a a = + = =  Also 4 1 3 a a d = +  2 3(3) 11 b b = + =  Question # 3 Let 1 2 3 4 5 , , , ,  A A A A A  and 6  are six A.Ms between 2 and 5. Then 1 2 3 4 5 6 2, , , , , , ,5  A A A A A  are in A.P. Here 1 2 a  =  and 8 5 a  =  1 7 5 a d + =  2 7 5 d + =  3 7 5 2 7 3 7 d d d = = =  So 1 2 1 3 17 2 7 7  A a a d = = + = + =  ( ) 2 3 1 3 6 20 2 2 2 2 7 7 7  A a a d = = + = + = + =  ( ) 3 4 1 3 9 23 3 2 3 2 7 7 7  A a a d = = + = + = + =  ( ) 4 5 1 3 26 12 4 2 4 2 7 7 7  A a a d = = + = + = + =  ( ) 5 6 1 3 15 29 5 2 5 2 7 7 7  A a a d = = + = + = + =  ( ) 6 7 1 3 18 32 6 2 6 2 7 7 7  A a a d = = + = + = + =  Hence 17 20 23 26 29 32 , , , , , 7 7 7 7 7 7  are six A.Ms between 2 and 5. Question # 4 Suppose 1 2 3 , ,  A A  and 4  are four A.Ms between 2 and 12 2 . Then 1 2 3 4 12 2 , , , , , 2  A A A A  are in A.P. Here 1 2 a  =  and 6 12 2 a  =  

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