Find b and then solve the equation

Question

3x2+bx+24=0, if one of its roots is 3

3x²+bx+24=0, if one of its roots is 3

Answer 1

3(3^2) + 3B + 24 = 0

 

3*9 + 3B + 24 = 0

 

27 + 3B + 24 = 0

 

 3b + 51 = 0

 

 B = -51/3 = -17

 

 

Check:

 

 3x^2 - 17x + 24 = 0

( 3x      -   8)( x  -      3  ) = 0

 

3 is indeed a root. so is 8/3