Question

solve for r
r^2+3r=8

Example r^2+3r=1
r=-3+√13/2,-3-√13/2

Answer 1

looks like the quadratic equation might help here

Answer 2

r^2 +3r -8 =0

a=1
b=3
c=-8

Use the quadratic formula to get your answer(s) for x.

Answer 3

The quadratic equation is where my problem lies

Answer 4

Do you know what the quadratic formula is?

Answer 5

http://0.tqn.com/d/create/1/0/i/9/9/-/Quadratic.formula.jpg

Answer 6

((-1) +/- sqrt ((3)^2-(4)(1)(-8)))/((2)(1))

Answer 7

(-1 +/- sqrt (41))/2

***THAT MEANS***

x = (-1 + sqrt(41))/2

x = (-1 - sqrt(41))/2

Answer 8

Thanks so much

Answer 9

This is what you do whenever factoring is impossible.

Answer 10

Or if you're too lazy to factor :-)... like I usually am LOL

Answer 11

so how would i put x^2+7x=10 into the quadratic equation

Answer 12

Okay so your format is going to be ax^2+bx+c

So with x^2+7x=10, you always always always get everything on the left side. You're setting it equal to zero.

x^2+7x-10=0

Now what are a, b, and c?

Answer 13

sorry typed problem wrong x^2+7x-10=0

Answer 14

k... so what do you think a, b, and c are?

Answer 15

a is 1
b is 7
c is 10

Answer 16

Yup!

Answer 17

I'll ask you one now. -x^2+2x+3

What is "a" in this case?

Answer 18

-1

Answer 19

yep

Answer 20

my problem is keeping it all in order

Answer 21

Now if there's a term, say b=-2 and you need to plug it into your formula, the first thing you're putting in is -b. So how to do that:

-(-2). So that will be a +2.

Answer 22

I understand. And I would recommend to do the problem in as many steps as you need to. And to slow down and pay close attention. I took an engineering problems course last quarter and I made a lot of mistakes when I didn't pay attention :-)

Answer 23

You can try that problem and we'll compare answers if you want.

Answer 24

ok is it -7+√89/2,-7-√89/2

Answer 25

That's what I got too. You know what you're doing!

Answer 26

You have no idea how much you have helped me thanks again!!!!!

Answer 27

I'm glad :-)

So step 1: Get everything on the left side so that it's set equal to zero.
step 2: write down what your a, b, and c values are
step 3: plug in to the formula and go slow

Answer 28

I truly cannot thank you enough I have been struggling for days

Answer 29

I would recommend Paul's online notes as an alternative to your book. Most algebra books truly suck.

http://tutorial.math.lamar.edu/Classes/Alg/SolveQuadraticEqnsII.aspx