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Graphing Radical Equations using a Table  Problem 1
Alissa Fong
Alissa Fong
MA, Stanford University
Teaching in the San Francisco Bay Area
Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts
You can always make graphs in Math class using a table of values. Sometimes it’s a little slower but it's usually on of the most accurate. So let’s go ahead and look at this problem where we are asked to find the domain of f(x) equals the square root of x plus 4 and sketch your graph using a table of values.
Okay so let’s talk about the domain. You know that the domain has to be values that make your radicand greater than or equal to 0. Radicand is the stuff under the square root. Be really careful it’s only the stuff under the square root, we don’t care about the stuff that’s outside the square root.
X plus 4, my radicand has to be greater than or equal to 0. So my domain is going to be all x values that are greater than or equal to 4, that’s my domain. So what that tells me is that when I’m creating my table, I don’t want to start my table like 7, 6, 5, 4 something like that, my table should start with 4.
Pick a few points then you're going to substitute them into your function one at a time and find your corresponding y values. I already did that ahead of time but I'll show you the first couple. If I put in 4 right there then I’ll have the square root of 4 plus 4 or the square of 0 which is 0. If I put in 3 I’ll have the square root of 1 which is 1. If I put in 2 I’ll have the square root of 2 which is approximately 1.4, if I put in 1 I’ll have the square root of 3 which is 1.7ish, and if I put in 0 I’ll have the square root of 4 which is 2.
Okay you can verify that on a calculator to get these decimal approximations. I’m ready to put these guys on the graph so here we go. I’m going to draw my graph which I think it’s going to look like the shape of a parabola kind of on its side. My first point was (4,0) then I had (3,1), (2,1.4), (1,1.7) and then (0,2). My parabola shape is on its side it goes like this and it's curvy. Please be careful again don’t stick an the arrow on that side. That’s like a dead end, that’s the last point or the smallest x value I could use in my domain. If I chose x number smaller than 4 I’d have nonreal solutions for my output.
So the shape of my graph looks like this what I did was find my domain before I made my table because that told me what x numbers to input to get my corresponding y output values.
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Alissa Fong
M.A. in Secondary Mathematics, Stanford University
B.S., Stanford University
Alissa has a quirky sense of humor and a relatable personality that make it easy for students to pay attention and understand the material. She has all the math tips and tricks students are looking for.
Your tutorials are good and you have a personality as well. I hope you have more advanced college level stuff, because I like the way you teach.”
Thanks alot for such great lectures... I never found learning this easier ever before... keep up the great work.... :)”
You seem so kind, it's awesome. Easier to learn from people who seem to be rooting for ya!' thanks”
Sample Problems (5)
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Graphing Radical Equations using a Table
Problem 1 3,237 viewsFind the domain of f(x) = √x + 4 and sketch a graph using a table of values.

Graphing Radical Equations using a Table
Problem 2 3,055 viewsFind the domain of f(x) = √x + 1 − 2 and sketch a graph using a table of values.

Graphing Radical Equations using a Table
Problem 3 2,439 viewsFind the domain of f(x) = √2x + 1 and sketch a graph using a table of values.

Graphing Radical Equations using a Table
Problem 4 519 views 
Graphing Radical Equations using a Table
Problem 5 475 views
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