que 11


11 .     Solve   the   equations   ( i )   log 5 x 4   +   5   -   log 1 / 5   x 2   +   25   =   3 2 ( ii )     log 5 x 4   +   5   -   log 1 / 5   x 2   +   25   =   3

i.log5x4+5-log1/5x2+25=32log5x4+5-log5-1x2+25=32Use logamb=1mlogablog5x4+5+log5x2+25=32Use logam+logan=logamnlog5x4+5x2+25=32x4+5x2+25=532x4+5x2+25=55Nowx2+2525x4+55Multiplyingx2+25x4+5125Thereforex4+5x2+25=55 has no solutionii.log5x4+5-log1/5x2+25=3log5x4+5-log5-1x2+25=3Use logamb=1mlogablog5x4+5+log5x2+25=3Use logam+logan=logamnlog5x4+5x2+25=3x4+5x2+25=53x4+5x2+25=125Nowx2+2525x4+55Multiplyingx2+25x4+5125125 is the minimum value of product which will occur when x2+25 and x4+5 are both minimumi.e. when x2+25=25, and x4+5=5So x=0 is the solution

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