Question

For the equation x^2 + 3x + j = 0, find all the values of j such that the equation has two real number solutions. Show your work.

Answer 1

j is less than or equal to 9/4 perhaps? My reasoning is that the discriminant must be greater than or equal to zero\[\sqrt{9-4(j)}\ge0\]

Answer 2

I believe there are infinite solutions as long as j is less than some critical number.

Answer 3

Right, discriminant, there ya' go.

Answer 4

So square both sides and solve

Answer 5

There are many. A couple are 2, -40, -54 etc.

Answer 6

How do i show my work?

Answer 7

Just write the formula for the discriminant and solve the inequality for j\[9-4j \ge0\]

Answer 8

Remember to reverse the inequality sign when you divide by negative four

Answer 9

@L.T. I dont know how to write a formula etc

Answer 10

My mistake, it's not truly a formula, but it is part of the Quadratic formula (the part under the radical). If you're writing an explanation in your answer, I advise that you begin by explaining that for a real solution of any quadratic equation the discriminant (the thing I wrote in my next to last response) must be greater than or equal to zero. Then you write out the discriminant as I wrote it and solve for j. Does that sound all right? Or am I just confusing you?

Answer 11

@L.T. I am not good at math and I really do not know what im doing

Answer 12

What do you need to know? I know some problems get to be tough, but you're actually doing one of the best things you can do by asking questions :)

Answer 13

\[j \le9/4\]

Answer 14

@TheMind, i know the answer is j less than or equal to 9/4 but i need to show work

Answer 15

@hartnn can you help me please?

Answer 16

Do you know how to factor?
Do you know the quadratic formula/about the discrimant?

Answer 17

no @livelaughlilz im not good at math

Answer 18

then what do you know about the problem? what did you learn in class?

Answer 19

the answer is j is less than or equal to zero 9/4. I im ood at math.. when i went to public school the teachers never help me and now i go to chool online so i dont understand very good

Answer 20

what did you learn about how to solve problems like this one?

Answer 21

i dont know...i dont understand nothing

Answer 22

what did you learn in class before you were given this homework problem?

Answer 23

i learned probability...probability has nothing with this eqation

Answer 24

you learned nothing about quadratic equations?

Answer 25

i dont understand math

Answer 26

have you learned anything about quadratic equations?

Answer 27

yes but i not remember because i didnot understand

Answer 28

khanacademy.org
you can relearn all the math you don't understand there. watch videos. you need knowledge before you can do this specific problem