My Math Forum quadratic formula...But this time with a negative

 Algebra Pre-Algebra and Basic Algebra Math Forum

January 19th, 2017, 02:35 PM   #1
Senior Member

Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

quadratic formula...But this time with a negative

says some thing about an I ?
Attached Images
 5.jpg (13.1 KB, 48 views)

January 19th, 2017, 02:40 PM   #2
Senior Member

Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

At this point now
Attached Images
 5.jpg (17.2 KB, 4 views)

January 19th, 2017, 02:48 PM   #3
Senior Member

Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

now here and stuck.
Attached Images
 5.jpg (16.6 KB, 2 views)

January 19th, 2017, 03:17 PM   #4
Senior Member

Joined: Sep 2015
From: USA

Posts: 2,496
Thanks: 1371

Quote:
 Originally Posted by GIjoefan1976 now here and stuck.
I don't know how they expect you to do these if you haven't been taught at least rudimentary complex numbers.

There exists a number generally called $i$

which is defined such that

$i^2 = -1$

so when you see something like $\sqrt{-444}$

this is $\sqrt{i^2 444} = i\sqrt{444}$

$i$ is the unit imaginary number, similar to the way $1$ is the unit real number.

The complex numbers are all numbers of the form $a + i b, ~a, b \in \mathbb{R}$

 January 19th, 2017, 03:55 PM #5 Math Team   Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038 Ya gotta be more careful, Joe me boy! Given equation is: (a - 8 )(a - 2) = -1 Simplifies to: a^2 - 10a + 16 = -1 Continue...
 January 19th, 2017, 04:30 PM #6 Math Team     Joined: Jul 2011 From: Texas Posts: 2,978 Thanks: 1573 $a^2-10a+17 = 0$ quadratic formula $a=1$, not $8$ $b=-10$ and $c=17$ $b^2-4ac = 100 - 4(1)(17) = 32$ now finish it ... you've been your own worst enemy by not paying attention to detail. Thanks from topsquark
January 19th, 2017, 09:36 PM   #7
Senior Member

Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

Quote:
 Originally Posted by romsek I don't know how they expect you to do these if you haven't been taught at least rudimentary complex numbers. There exists a number generally called $i$ which is defined such that $i^2 = -1$ so when you see something like $\sqrt{-444}$ this is $\sqrt{i^2 444} = i\sqrt{444}$ $i$ is the unit imaginary number, similar to the way $1$ is the unit real number. The complex numbers are all numbers of the form $a + i b, ~a, b \in \mathbb{R}$
Thanks for sharing and teaching me this, it will be for sure something I will pass on to my tutors!

January 19th, 2017, 09:56 PM   #8
Senior Member

Joined: Sep 2015
From: USA

Posts: 2,496
Thanks: 1371

Quote:
 Originally Posted by GIjoefan1976 Thanks for sharing and teaching me this, it will be for sure something I will pass on to my tutors!
that's all well and good but the point a couple others have made is that you wouldn't have run into this if you hadn't messed up the algebra.

So it makes more sense that you hadn't seen complex numbers yet.

You'd have seen them eventually.

January 25th, 2017, 10:14 AM   #9
Senior Member

Joined: Feb 2016
From: seattle

Posts: 377
Thanks: 10

Quote:
 Originally Posted by romsek that's all well and good but the point a couple others have made is that you wouldn't have run into this if you hadn't messed up the algebra. So it makes more sense that you hadn't seen complex numbers yet. You'd have seen them eventually.
Thanks Yes I still make mistakes but the video that was given to me by My math class said I would be dealing with a negative so When i got what was above I thought I had gotten the situation I was meant to get.

 January 25th, 2017, 04:04 PM #10 Math Team   Joined: Jan 2015 From: Alabama Posts: 3,264 Thanks: 902 Your basic problem, GIJoefan1986, is that you multiplied (x- 8 )(x- 2) and got $8^2- 10x+ 17$ rather than $x^2- 10x+ 17$! Where in the world did that $8^2$ come from?

 Tags formulabut, negative, negitive, quadratic, time

 Thread Tools Display Modes Linear Mode

 Similar Threads Thread Thread Starter Forum Replies Last Post Youi Math 2 March 10th, 2016 12:26 AM markaval1966 Algebra 3 February 22nd, 2016 09:33 AM -Duir- Economics 1 March 26th, 2013 07:30 PM kkelley Algebra 4 June 12th, 2012 09:56 AM 312 Algebra 2 September 15th, 2008 03:23 PM

 Contact - Home - Forums - Cryptocurrency Forum - Top