Question

If 3 is a solution of 3x square +(k-1)x+9=0,then k=?

Answer 1

3x²+(k-1)x+9=0
Substitute the value of 3 instead of x,
   3*3²+(k-1)3+9=0
    27+3k-3+9=0
    24+9+3k=0
     33+3k=0
       3k=0-33
       3k=-33
        k=-33/3
         k=-11