Help me factorise
 
a^3 -a-120

Asked by tejvarun | 21st Aug, 2016, 09:55: AM

Expert Answer:

begin mathsize 16px style straight a cubed minus straight a minus 120
equals straight a cubed minus straight a minus 125 plus 5
equals straight a cubed minus 125 minus straight a plus 5
equals left parenthesis straight a cubed minus 5 cubed right parenthesis minus left parenthesis straight a minus 5 right parenthesis
equals left parenthesis straight a minus 5 right parenthesis left parenthesis straight a squared plus 5 straight a plus 25 right parenthesis minus left parenthesis straight a minus 5 right parenthesis
equals left parenthesis straight a minus 5 right parenthesis left parenthesis straight a squared plus 5 straight a plus 25 minus 1 right parenthesis
equals left parenthesis straight a minus 5 right parenthesis left parenthesis straight a squared plus 5 straight a plus 24 right parenthesis end style

Answered by Rashmi Khot | 22nd Aug, 2016, 11:16: AM