Quick discriminant question (1 Viewer)

[LoveHateSchool]

For what values of k will x^2=(k+3)x + k have real roots?

I've made a mistake somewhere in the working because when I tried to factorise the brackets, it didn't work.

Rep and hugs for help

 

[pwoh]

(k+3)^2 - 4k > 0
k^2 + 6k + 9 - 4k > 0
k^2 + 2k + 9 > 0
(k+1)^2 + 8 > 0

true for all real k

 

[jnney]

For what values of k will x^2=(k+3)x + k have real roots?

I've made a mistake somewhere in the working because when I tried to factorise the brackets, it didn't work.

Rep and hugs for help

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

triangle (lmao) = (k+3)^2 + 4k

for real roots: triangle >=0

k^2 + 6k + 9 + 4k >=0

K^2 +10k + 9 >=0

(k+9)(k+1) >= 0

K=<-9 or K>= -1

 

[newb1234]

(k+3)^2 - 4k > 0
k^2 + 6k + 9 - 4k > 0
k^2 + 2k + 9 > 0
(k+1)^2 + 8 > 0

true for all real k

lol idiot, another 4unit maths noob.

You did 4unit maths and still make mistakes, add another person to the list. 4unit students are massive noobs at 2unit.

 

[SpiralFlex]

(k+3)^2 - 4k > 0
k^2 + 6k + 9 - 4k > 0
k^2 + 2k + 9 > 0
(k+1)^2 + 8 > 0

true for all real k

Just a minor hiccup.



For real roots,

 

[jnney]

For real roots,

beat you to it ^_^

 

[SpiralFlex]

beat you to it ^_^

I was watching X Factor...

 

[newb1234]

Just a minor hiccup.

For real roots,

For someone that did 4unit maths last year and is doing science (most likely maths) at uni, it is UNACCEPTABLE.

 

[Drongoski]

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

triangle (lmao) = (k+3)^2 + 4k

for real roots: triangle >=0

k^2 + 6k + 9 + 4k >=0

K^2 +10k + 9 >=0

(k+9)(k+1) >= 0

K=<-9 or K>= -1

jnney

The triangle is called "delta"

 

[Alkanes]

change

 

[LoveHateSchool]

Thank you! I expanded with -(k+3) instead of just (k+3)

 

[jnney]

jnney

The triangle is called "delta"

I'm sorry........I've only been sleeping for 5 hrs /night this past week..

 

[SpiralFlex]

If you are bored here's a good exercise for you. Learning the Greek Alphabet is fun.