Relation between A.M., G.M. and H.M. - Practice Questions & MCQ

Updated on Sep 18, 2023 18:34 AM

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Properties of A.M. and G.M.

Properties of A.M. and  G.M

A and G are arithmetic and geometric mean of ‘a’ and ‘b’, two real, positive and distinct number. Then,

  • a and b are the roots of the equation x2-2Ax+G2=0.

  • a and b are given by A \pm \sqrt{(A+G)(A-G)}.

Proof:

\begin{array}{l}{A=\frac{a+b}{2} \Rightarrow 2 A=a+b} \\ {G=\sqrt{a b} \Rightarrow G^{2}=a b}\end{array}

a and b are the roots of the equation, then

\begin{array}{l}{x^{2}-2(\text { sum of roots) } x+\text { products of roots }=0} \\ {\Rightarrow x^{2}-(a+b)+a b=0} \\ {\Rightarrow x^{2}-2 A x+G^{2}=0}\end{array}

Roots of the equation are 

\begin{array}{l}{x=\frac{2 A \pm \sqrt{(-2 A)^{2}-4 \cdot 1 \cdot G^{2}}}{2}} \\ {{x}=A \pm \sqrt{(A+G)(A-G)}}\end{array}

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Properties of A.M. and G.M.

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Properties of A.M. and G.M.

Mathematics for Joint Entrance Examination JEE (Advanced) : Algebra

Page No. : 5.12

Line : 55

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