(-7/2 + √17/2) ≈ -1.438 and (-7/2 - √17/2) ≈ -5.562
53
3 5 7 11 13 17 19
17
The two numbers you multiply together to equal 391 are 17 by 23.
-1
-241
1 and 17.
-17
17
Not sure about 720 but if the answer were to be 72 then the two numbers are 8 and 9 8 x 9 = 72 8 + 9 = 17
-17