# Find the coordinates of these points..

• Sep 9th 2010, 02:34 PM
gabriel
Find the coordinates of these points..
two different points on the line y=2 are each exactly 13 units from the point (7,14). Draw the picture of this situation, and then find the coordinates of these points.

^so i tried setting up a cartesian coordinate plane and set the points out but i didnt know what else to do. experts?
• Sep 9th 2010, 02:44 PM
Plato
Quote:

Originally Posted by gabriel
two different points on the line y=2 are each exactly 13 units from the point (7,14). Draw the picture of this situation, and then find the coordinates of these points.

^so i tried setting up a cartesian coordinate plane and set the points out but i didnt know what else to do. experts?

Solve $\sqrt{(x-7)^2+(12)^2}=13$ for $x$.
You should find two values.
• Sep 9th 2010, 02:57 PM
gabriel
i got stuck on sqrt -13x + 158 = 13
^ and would x be an (i) integer?
• Sep 9th 2010, 03:01 PM
Plato
Quote:

Originally Posted by gabriel
i got stuck on sqrt -13x + 158 = 13

The part is red is comply wrong.
You need to learn to do basic algebraic operations.
• Sep 9th 2010, 03:20 PM
gabriel
^how is this wrong?

ok so the problem is sqrt of (x-7)^2 + 12^2=13
so to solve this is did the following:
foiled (x-7)^2 = x^2+14x+14
while doing that, the problem would be sqrt of x^2-14x+14 (+) 144 = 13
and so on what is wrong with that?
• Sep 9th 2010, 03:39 PM
Plato
Quote:

Originally Posted by gabriel
ok so the problem is sqrt of (x-7)^2 + 12^2=13
so to solve this is did the following:
foiled (x-7)^2 = x^2+14x+14
while doing that, the problem would be sqrt of x^2-14x+14 (+) 144 = 13
and so on what is wrong with that?

FOIL, in my view, is a useless idea.
$(x-7)^2=(x-7)(x-7)=x^2-7x-7x+49=x^2-14x+49$

If you cannot do these simple operations, then you are going to have a most difficult time doing pre-calculus.
• Sep 9th 2010, 03:47 PM
Quote:

Originally Posted by gabriel
^how is this wrong?

ok so the problem is

$\sqrt{(x-7)^2 + 12^2}=13$

so to solve this is did the following:

foiled (x-7)^2 = x^2+14x+14 .....this is incorrect, you should be multiplying the -7's..not adding 7+7

while doing that, the problem would be sqrt of x^2-14x+14 (+) 144 = 13
and so on what is wrong with that?

$(x-7)^2=(x-7)(x-7)=x(x-7)-7(x-7)=x(x)+x(-7)-7(x)-7(-7)$

$=x^2-7x-7x+49=x^2-14x+49$

$x^2-14x+49=(13)^2$

Also $x^2-14x$ is not equal to $-13x$

$x-14x=-13x$
• Sep 9th 2010, 03:59 PM
gabriel
so what do i do when i get
sqrt of x^2-14x+49 = 13^2 or (169)
• Sep 9th 2010, 04:44 PM
Plato
You do not understand this problem at all do you?