[0645] Flashbacks
└ posted on Monday, 29 December 2014, by Novil
- Sandra: Luna, you asked quite a few very weird questions in math today again.
- Luna: … Sorry.
- Sandra: Should I come over after school to help you study?
- Luna: That would be very kind. Thank you.
- Sandra: No problem. We all will get something out of it after all.
- Luna: How so?
- Sandra: The screams of terror of our old math teacher when you tried to factorize 49x² – 28 + 4 on the blackboard still haunt me every night.
- Luna: The doctor said he may eventually be able to look at numbers again without getting flashbacks.
![[0645] Flashbacks](/comics/2014-12-29-0645-flashbacks.png "[0645] Flashbacks")
@ Harmon:
actually both forms are used. One way in the comic strip and the other in the text. Duh. Just noticed that after I answered.
I know I’m a little late to this discussion and probably nobody will even read this but my inner mathematician just can’t shut up:
First of all: Yes, you can solve this problem by just using the binomial formula.
But it is also possible to use the quadratic formula. For this method you first must assume that 49x^2-28x+4=0 and then calculate the zeros with the quadratic formula. This will get you 2/7 as a double zero of this function.
Now we need to remember that you can write a quadratic polynomial only using its zeros and the coefficient of x^2 which in this case results in
49x^2-28x+4=49(x-2/7)^2.
But remembering that 49=7^2 you can write this as 49(x-2/7)^2=(7x-2)^2 which is the same result you get by using the binomial formula.
So, in essence, (almost) everyone was right, isn’t that nice!
Euklid wrote:
No because it NEVER said solve. it said first to expand which was then corrected to facorized. so Never in essence was assuming it equals zero right.
Factorize it? Uh… let’s see… that’s just (7x – 2)^2. Right? It’s not that horrifying… o.o
@ Autoskip:
But its an expression!
How is she alive!
WaffleFox wrote:
There are people who are not good at math. And it builds up since if you don’t really understand the basics you will have even more problems to understand new concepts. Also if you are called to the blackboard in a subject you have a history of being bad in you’ll get nervous and will likley make mistakes that you wouldn’t make otherwise.
For the problem/task itself: Factorising does not need an equationmark (that task would be solve).
Ah, factoring… For some bizarre reason I never learned to factor equations in highschool, had to wait for college to learn that. Instead we had to use that painful quadratic equation. (7x-2)² is easy to find.
JuyJuka wrote:
The question is factorisation, not solving. 49x^2 – 28x + 4 factorised is (7x – 2)(7x – 2). Solving with these can only be done if it’s equal to zero, otherwise it can’t be done. Or at least is really damn hard to do. If it’s 49x^2 – 28x + 4 = 0, then (7x – 2) must equal zero, therefore 7x = 2 therefore x = 2/7
I believe it’s somewhere around -3.048883e+29
(7x-2)(7x-2)
JuyJuka wrote:
Just pretend it = 0
That’s usually the point of teaching factoring anyway
**Spoiler**
x=1/7 if you assume 49x² – 28 + 4=0
@ XaosPheonix:
oops, I meant 2/7 not 1/7, my bad.
@ JuyJuka: You’re supposed factor it. Thinking back to Algebra II is hard, I know.
How the F*CK does one factorize a quadratic equation without solving it?
Aleck493 wrote:
I had very similar problems. Thing is, my mind does higher level math on instinct. I just look at an equation and the answer is just “there”. Got to the point that I was teaching myself Analytic Geometry in 6th grade (age 11) because math class was boring beyond belief. (for my 5th grade science project I proved Ohm’s Law) I couldn’t show my work because there was no work to show… I just “knew”.
The burdens of the gifted…
i think its easy, its 12 grade math if you think, i mean its quadratic so all you have to do is split the number with both variable and consonant in two parts like say 6x becomes 4x + 2x and then use common system so if the number was 8x²+ 6x +1 the answer will be 8x²+4x+2x+1= 4x(2x+1)+1(2x+1)=(2x+1)(4x+1) hemce x will have two values in this case, one being 2x=-1=>X=-½ as well as 4x=-1=>X=-¼
roguebfl wrote:
of course (-7x+2)^2 also works