Easy math quiz

[wolfson]

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.

[psi20]

0=4x^2 - 12x - 4

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

0=x^2-3x-1

 

(3+/-sqrt13)/2

[Leison]

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

[Dave]

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

[wolfson]

lol yes

[Dave]

In that case I won't bother doing it then

[Primarygun]

Need I wait for another week to post question ?

[Dave]

Say what now?

 

You can post questions anytime you like.

[Guest mathfreak]

Test post. This is my first visit here.

 

cheers.

[Severian]

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

[paganinio]

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'

[Guest tenlientl]

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?

[jordan]

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.

[Dave]

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.

[dash00]

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.

[BigMoosie]

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.

[TheGeek]

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