Have to choose 2 numbers in which their product is 18, and their sum is 9, therefore both have to be negative numbers.
ab = 18 a+b = 9
18 = 2 *9 = 6* 3 , so 63 = 18 , 63 =9
Split 9X to 6x 3X
9 X^{2 } 9x +2 =0
9 X^{2}  6X  3X + 2 = 0
3X ( 3X  2 )  ( 3X 2 ) = 0 factor by grouping
( 3 X  2 ) ( 3X 1 ) =0
3X  2 = 0 X = 2/ 3 3X 1 = 0 X = 1/3
This is a general rule:
aX^{2 }+ bX + c = 0
choose 2 numbers m,n in such away
that ac = mn and b/a = m+n
where you have the values of a,b,c given in a quadratic equation.
If m.n are integer values, then you can factor like the above example, otherwise use quadratic formula:
Oct 1

Parviz F.