Question 1179409
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The other tutor showed a derivation for the answer:<br>
The inverse of {{{(ax+b)/(cx+d)}}} is {{{(b-dx)/(cx-a)}}}<br>
This particular kind of inverse is encountered often, especially in timed math competitions.  While the derivation is not very complicated, it takes time and effort.  It might be worthwhile to memorize the answer.<br>
Write the inverse in a slightly different form:<br>
The inverse of {{{(ax+b)/(cx+d)}}} is {{{(-dx+b)/(cx-a)}}}<br>
Note the pattern: The b and c stay where they are; the a and d switch places and switch signs.<br>