Question 174578
{{{matrix(1,3,3/(a^2 + a), "×",  (2a + 2)/6)}}}
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Factor {{{a^2+a}}} as {{{a(a+1)}}}
Factor {{{2a+2}}} as {{{2(a+1)}}}

{{{matrix(1,3,3/(a(a + 1)), "×",  (2(a + 1))/6)}}}

Indicate the multiplication of the numerators
and denominators:

{{{(3*2(a+1))/(6a(a + 1)) }}}

Cancel the {{{3*2}}} and the {{{6}}}.
Cancel the {{{(a+1)}}}'s
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  1    1
{{{(cross(3*2)(cross(a+1)))/(cross(6)a(cross(a + 1))) }}}
  1   1
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So all that's left is:

   {{{1/a}}}

Edwin</pre>