If a=log245⁡175 and b=log1715⁡875 then the value of 1−aba−b is

a=log5⁡175log5⁡245=2+log5⁡71+2log5⁡7 or  a+2alog5⁡7=2+log5⁡7 or  log5⁡7=a−21−2a----i Now b=log5⁡875log5⁡1715=3+log5⁡71+3log5⁡7or  b+3blog5⁡7=3+log5⁡7or log5⁡7=b−31−3b----iiFrom Eqs. (i) and (ii), we get a−21−2a=b−31−3b⇒ 1−aba−b=5