Question 9289
The problem says "do NOT combine fractions."  Just find the LCD.  

{{{12/(5a^2)}}} and {{{ 9/(a^3)}}}


The LCD must have all the factors of all the denominators.  Also, you have to know that a^2 is a factor of a^3, so if you have a factor of a^3, that takes care of the a^2 also.  See my Lesson Plan called "Least Common Denominators" for more explanation and examples, and also my own website for free sections of explanation under Basic Algebra.  Anyway, for this problem, the LCD must have {{{5a^3}}}.  This might be the final answer for this problem.  However, I'll go to the next step just in case!


In the first fraction, your denominator has a 5 factor and an a^2 factor, but it needs another factor of "a" to bring it up to the LCD.  So multiply the first fraction, numerator and denominator, by "a":
{{{(12/(5a^2))* (a/a) }}} = {{{12a/(5a^3) }}}


For the second fraction, you have the a^3 factor, but you are missing the factor of 5.  So multiply the numerator and denominator of the second fraction by 5:

{{{ (9/(a^3)) * (5/5) }}} = {{{45/(5a^3)}}}


According to the instructions in this problem, you are not supposed to put the fractions together.  So that should do it, right?


R^2 at SCC