Question

if 3 is the solution of equation 3 X square +( K - 1)x + 9 equal to zero then find k​

Answer 1

hope this helps you
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Answer 2

${3x}^{2} + (k - 1)x + 9 = 0 \\{3x} + (k - 1)+ 9 = \frac{0}{x} \\{3x}+ (k - 1)= - 9 \\{3x}+ (k )= - 9 - 1 \\{3x} + k= - 10 \\{x} = \frac{ - 10 - k}{3}$

put x into 2nd last step