Generating random numbers based on a +/- input

I’d like to generate a random number in a given range based on an input of positive or negative. The positive input would pick a positive number between x and y (4 and 42 actually), the negative between -6 and -72. In other words, if input+ rand(4,42), if input- rand(-6,-72), I’m just not sure how to string it all together !!

Many thanks in advance !!!