Determine k if -3 is a root of 2x^2 +kx + 9 =0?

Question

I dont even know what that means, but can someone please show how to do it step by step?

Answer 1

If -3 is a root, then letting x=-3 should make the right side equal 0.

2(-3)^2+k(-3)+9=0

27-3k=0

k=9

Answer 2

Given that -3 is the root of the equation 2x²+kx+9=0
therefore x=-3 will satisfies the equation 2x² +kx+9=0
Now put x=-3 in the given equation 2(-3)²+k(-3)+9=0
i.e.18-3k+9=0
i.e.27-3k =0
thus 3k=27
hence k=27/3=9
therefore k=9

Answer 3

Okay, first look at the equation: 2x² + kx + 9 = 0
the x in the above equation is called the 'root' of the equation.

So, they already give you the root (x = -3) and they want you to find the value for k.

So, first you substitute x = -3 into the equation:

2(-3)² + k(-3) + 9 = 0
18 - 3k + 9 = 0

All you basically have to do now is rearrange for k:

3k = 27
k = 9

Answer 4

It means that a solution of equation is x = - 3
Therefore:-
2 (-3)² - 3k + 9 = 0
18 - 3k + 9 = 0
27 = 3k
k = 9

Answer 5

Substitution: 2(-3)^2 + k(-3) + 9 = 0.
2(9) -3k +9 = 0
27 = 3k
k = 9.

Answer 6

certo hai raggiona perchè sendo:5+6-47=a3. hai capito?