Tutor.com Quadratic Functions Session

Oct. 28, 2013

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Session Transcript - Live Math Tutoring - MTH/209, 10/20/2013 1:42PM - Tutor.comSession Date: 10/20/2013 1:42PM
Length: 21.6 minute(s)
Subject: Live Math Tutoring - MTH/209


System Message
[00:00:00] *** Please note: All sessions are recorded for quality control. ***

FELICIA (Customer)
[00:00:00] Find the vertex of the parabola. f(x)=x^2-8x-5

Jonas W (Tutor)
[00:00:17] Welcome to tutor.com . Hello :)
[00:00:20] How are you today?

FELICIA (Customer)
[00:00:35] hi. fine. how about yourself?

Jonas W (Tutor)
[00:00:54] Great
[00:01:00] Let's get started

FELICIA (Customer)
[00:01:04] ok

Jonas W (Tutor)
[00:01:29] What have you learned so far about finding the vertex of a parabola

FELICIA (Customer)
[00:02:02] nothing yet. going to class tomorrow. Have to do assignment today.

Jonas W (Tutor)
[00:02:09] Ok
[00:02:38] One way to find the vertex of a parabola requires the following rule: x at the vertex = -b/2a
[00:02:44] Are you familiar with that idea?

FELICIA (Customer)
[00:03:05] I've seen a problem like that before

Jonas W (Tutor)
[00:03:19] Ok
[00:03:32] So, in this problem : a = ? b = ? c = ?

FELICIA (Customer)
[00:03:46] ok

Jonas W (Tutor)
[00:04:47] Are you with me so far?

FELICIA (Customer)
[00:05:02] I am following

Jonas W (Tutor)
[00:05:16] So, in this problem, what would a equal?

FELICIA (Customer)
[00:05:35] 1?

Jonas W (Tutor)
[00:05:47] Good
[00:05:59] The 1 is "understood"
[00:06:01] b= ?

FELICIA (Customer)
[00:06:15] -8?

Jonas W (Tutor)
[00:06:24] Good again!
[00:06:32] So, -b/2a equals?

FELICIA (Customer)
[00:07:09] -16?

Jonas W (Tutor)
[00:07:48] The numerator is - (-8) which equals ?
[00:08:30] One minus sign from the formula
[00:08:42] and the other minus sign because it's -8
[00:08:52] So, what does that equal?

FELICIA (Customer)
[00:09:08] 2?

Jonas W (Tutor)
[00:09:14] Isn't the numerator + 8

FELICIA (Customer)
[00:09:20] yes

Jonas W (Tutor)
[00:09:38] And the denominator is 2 times 1 which as you said is 2a or just plain 2

FELICIA (Customer)
[00:09:48] ok

Jonas W (Tutor)
[00:09:54] So, 8/2 = ?

FELICIA (Customer)
[00:10:01] 4

Jonas W (Tutor)
[00:10:06] Good
[00:10:13] So, the x coordinate of the vertex is 4

FELICIA (Customer)
[00:10:24] ok

Jonas W (Tutor)
[00:10:29] Now, to find the y coordinate
[00:10:41] we have to calculate f(x) in the original equation
[00:10:51] by substituting 4 instead of x
[00:11:00] Do you want to show that step?

FELICIA (Customer)
[00:11:12] yes

Jonas W (Tutor)
[00:11:31] Go ahead, let me see your work
[00:11:38] You can continue on the whiteboard

FELICIA (Customer)
[00:11:49] not clear of what to do.

Jonas W (Tutor)
[00:12:35] I copied the formula for the equation
[00:12:54] now wherever you see x, you substitute 4 with a parentheses
[00:13:04] Does that get you started on that step?

FELICIA (Customer)
[00:13:37] ok. is that ok?

Jonas W (Tutor)
[00:13:42] Good, continue with the -6
[00:13:45] -5

FELICIA (Customer)
[00:13:55] -5 where?

Jonas W (Tutor)
[00:14:19] Do you see where I'm pointing?
[00:14:32] Bring down the -5 from the equation

FELICIA (Customer)
[00:14:41] ok. msg box covered.

Jonas W (Tutor)
[00:14:58] Good
[00:15:06] One point
[00:15:19] The first parentheses should be around just the 4
[00:15:25] not the 4 squared
[00:15:28] Let me show you

FELICIA (Customer)
[00:15:51] ok

Jonas W (Tutor)
[00:16:01] Good :)
[00:16:07] Now, finish the math
[00:16:12] (4) ^2 is ?
[00:16:22] and - 8(4)
[00:16:25] and -5

FELICIA (Customer)
[00:16:55] )4)^2= 16

Jonas W (Tutor)
[00:17:04] Good
[00:17:09] Go ahead and continue on the board
[00:17:54] 8 times 4
[00:18:01] is ?
[00:18:42] Good
[00:18:54] Good
[00:19:02] and 16 - 32 - 5 is ?
[00:19:45] Good .
[00:19:55] So the y coordinate of the vertex is -21
[00:20:03] so, the vertex in (x,y) form is?

FELICIA (Customer)
[00:20:18] is (4, -21)

Jonas W (Tutor)
[00:20:27] Good work!
[00:20:40] Do you have any questions on that before I log off?

FELICIA (Customer)
[00:20:46] yeah.Thanks

Jonas W (Tutor)
[00:20:59] Thanks for using tutor.com :)

FELICIA (Customer)
[00:21:02] Have a great day

Jonas W (Tutor)
[00:21:10] I'd appreciate it if you would fill out the survey.

FELICIA (Customer)
[00:21:13] Will do

Jonas W (Tutor)
[00:21:19] Same to you. Bye :)