Question

find K if 3is a solution of 3x ²+(k-1)x+9=0

Answer 1

3x3x3 + (k-1)3 +9=0
27 + 3k - 3 +9
27 + 3k +6=0
33 +3k=0
3k=-33
k=-11

Answer 2

3(3)²+(k-1)3+9 = 0
=>3×9+3K-3+9 = 0
=>27+3K+6 = 0
=>3K+33 = 0
=>3K = -33
=>K = -33/3
k = -11