apabila x=3 merupakan solusi dari persamaan 3x² + ( k - l )x + 9 = 0 , maka nilai k samadengan

3x² + ( k - l )x + 9 = 0
3(3²) + ( k - l )3 + 9 = 0
3.9 + 3k - 3l + 9 = 0
27 + 9 + 3k - 3l = 0
36 + 3k - 3l = 0
misal : k = -4, dan l = 8
3(3²) + (-4 - 8)3 + 9 =0
27 + -12(3) + 9 = 0
27 + 9 - 36 = 0
36 - 36 = 0
K = -4

x=3
3(3²) + (k-1) 3 +9 = 0
3.9 + 3k-3 + 9 = 0
27 +3k-3 + 9 = 0
3k + 33 = 0
3k = -33
k= -33/3
k = -11