#\frac { 7} { x ^ { 2} } + \frac { 1} { x } - \frac { 5} { x ^ { 2} } + \frac { 3} { x }#
#=>\frac{7}{x^2}-\frac{5}{x^2}+\frac{1}{x}+\frac{3}{x}# -----grouping like terms.
#=>\frac {7-5} {x ^2} + \frac {1+3} {x} #
#=>\frac {2} {x ^2} + \frac {4} {x} #
#=> \frac {2} {x ^2} + \frac {4} {x}(x/x) # ------ making denominators equal
#=>\frac {2} {x ^2} + \frac {4x} {x^2} #
#=>\frac {2+4x} {x ^2} #