solve the polynomial equation
(x+5)(x+1)=45
You can expand the left-hand side and transfer the 45 to the left to make a quadratic equation which you can solve by factoring.
You can also find a solution by inspection, noting that 5-1=4, and if you can find two factors of 45 that differ by 4, then these factors are the values in the parentheses on the left. Thus solve for x by inspection.