Question 362365
Use a common denominator, {{{x(x-3)}}}
{{{3/(x-3)-1/x=(3x)/(x(x-3))-(x-3)/(x(x-3))}}}
{{{3/(x-3)-1/x=(3x-(x-3))/(x(x-3))}}}
{{{3/(x-3)-1/x=(3x-x+3)/(x(x-3))}}}
{{{highlight(3/(x-3)-1/x=(2x+3)/(x(x-3)))}}}

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Use the common denominator {{{(x^2+5)(x+5)}}}
{{{(4x+1)/(x+5)+10/(x^2+5)=((4x+1)(x^2+5))/((x+5)(x^2+5))+(10(x+5))/((x+5)(x^2+5))}}}

{{{(4x+1)/(x+5)+10/(x^2+5)=((4x+1)(x^2+5)+10(x+5))/((x+5)(x^2+5))}}}
{{{(4x+1)/(x+5)+10/(x^2+5)=((4x^3+20x+x^2+5)+10x+50))/((x+5)(x^2+5))}}}
{{{highlight((4x+1)/(x+5)+10/(x^2+5)=(4x^3+x^2+30x+55)/((x+5)(x^2+5)))}}}