MHB Solve Quadratic Equation: 3x²+12x+c=0

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To determine the number of solutions for the quadratic equation 3x² + 12x + c = 0, the discriminant (D) must be analyzed. The discriminant is calculated as D = 12² - 4(3)c. For there to be one real solution, D must equal zero; for two real solutions, D must be greater than zero; and for two nonreal (complex) solutions, D must be less than zero. Solving the discriminant equation for c provides the specific values that correspond to each scenario. Understanding these conditions is essential for solving the quadratic equation effectively.
PhantomTechnic
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Hello I've been stuck on this test review question for a few days, and I can't figure it out. Can someone help out?
"3x²+12x+c=0, Find solutions for c, where there is 1 real solution, 2 real solutions, and 2 nonreal(complex) solutions"
 
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Hello and welcome to MHB, PhantomTechnic! (Wave)

Let's review the quadratic formula:

Given the quadratic equation:

$$ax^2+bx+c=0$$

Then the solution is given by:

$$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$

Now, looking at that formula, what condition do we need for there to be only 1 solution?
 
MarkFL said:
Hello and welcome to MHB, PhantomTechnic! (Wave)

Let's review the quadratic formula:

Given the quadratic equation:

$$ax^2+bx+c=0$$

Then the solution is given by:

$$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$

Now, looking at that formula, what condition do we need for there to be only 1 solution?
Wouldn't it be when it equals zero?
 
PhantomTechnic said:
Wouldn't it be when it equals zero?

When what equals zero? You are headed in the right direction, but I want to make certain you are talking about the correct expression...D
 
To answer Mark, D = 12² - 4(3)c, where D is the discriminant. What equals 0?
Solve for c. What do you get? It's probably not a prime number!
 
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