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If `a ,b ,c`are three distinct real numbers in G.P. and `a+b+c=x b ,`then prove that either x < -1 or x > 3 |
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Answer» `a+b+c = xb` `=>xb-b = a+c` `=>b(x-1) = a+c` `=>x-1 = (a+c)/b` As, `a,b,c` are in G.P, `:. b^2 = ac => b = sqrt(ac).``:. x-1 = (a+c)/(sqrt(ac))` `=>x -1 = sqrt(a/c)+sqrt(c/a)` Now, we know, `m+1/m gt 2` or `m+1/m lt -2.` `:. sqrt(a/c)+sqrt(c/a) gt 2 or sqrt(a/c)+sqrt(c/a) lt -2.` `:. x - 1 gt 2 or x-1 lt -2` `=>x gt 3 or x lt -1.` |
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