Ok im going to have a go at holding a quiz........

 

Q:

 

Factorise completely the expression:

 

f(x) = 3x^2 + x^2 - 12X -4, and hence solve the equation f(x) = 0.

 

Ok try and solve the question, and gl to you all....

 

Winners will be announced in 2 days.

0=4x^2 - 12x - 4

0=4(x^2 - 3x - 1)

0=x^2-3x-1

 

(3+/-sqrt13)/2

f(x)=3x^2+x^2-12x-4

=4x^2-12x-4

=4(x^2-3x-1)

f(x)=0 {given}

so we can write,

 

4(x^2-3x-1)=0

(x^2-3x-1) =0 {4<>0}

 

using formula, we have

 

x=3.3 or -.3

Since you have f(x) defined to be the function 3x² + x² - 12X -4, can we assume x = X?

lol yes

In that case I won't bother doing it then

Need I wait for another week to post question ?

Say what now?

 

You can post questions anytime you like.

Test post. This is my first visit here.

 

cheers.

Did you perhaps mean: f(x) = 3 x³ + x² - 12 x - 4 ?

 

If so, f(x) = (x²-4)(3x+1) = (x-2)(x+2)(3x+1)

 

f(x) = 0 => x = -2, +2, or -1/3

Reasonable

Cheers, Severian

 

Just like a question which has been given the 'official answer',but in fact there's more to think about.

 

There're 2 evidences that Severian is right.

1,The original question is weird.'f(x) = 3x^2 + x^2 - 12X -4'=0

2,The original answer is also a little weird.'(3+/-sqrt13)/2'

Whoa...... This is veyr shocking. I don't get all these f(x) and stuff. I'm in grade 11. Is it normal for a grade 11 to not know this?

Normal is rather tough to define. I've know about it since probably 9^th grade, but there are others in 12^th with me who still don't know. The f(x) is probably what you normaly call y. As in y=2x is the same as f(x)=2x. f(x) basicaly says that for a given value of x, what is the result of the function.

In more depth, f is a function which takes a variable (or perhaps more than one variable in some cases), and by performing an operation on it converts it to some other number.

Whoa...... This is veyr shocking. I don't get all these f(x) and stuff. I'm in grade 11. Is it normal for a grade 11 to not know this?

 

depends what level of maths you do, i was confused by using f(x) as opposed to y= when we were first taught to use it, which was at the begining of year 11.

It doesnt have to always be f, it can be any other variable or even word such as the well know trig functions. You recognise the notation of sin(30) = 1/2, as you see, one or more numbers in, but always only one number out.

f(x) = 3x^2 + x^2 -12x -4

f(x) = 4x^2 - 12x - 4

f(x) = 4(x^2 - 3x 1)

 

using the quadratic formula you could figure out that f(x) is either 3.309 or -.309