radical equations: (square root of x-1)=x-3

[jburgswife30]

(square root of x-1)=x-3

x-1^2=x-3^2
x-1=x^2-2x-9
x^2-x-8=0
(x-8)(x-1)=0
x=8
x=1

Now I am pretty sure this is wrong, can anyone tell me where I messed up.

I am also having trouble with this one

(2xsquare root of 2x)(3squareroot of 5x)

so it looks something like this ( i don't know how to do the square root sign)

(2x 2x)(3 5x)

do I use the foil method for this, I am not even sure where to start

 

[jburgswife30]

I figured out the first one, so I am working on the second one now.

 

[jwpaine]

\(\displaystyle \L (2x \sqrt{2x})(3 \sqrt{5x}) = 0\)

No foil, only multiply once

\(\displaystyle \L 6x \sqrt{2x} \sqrt{5x} = 0\)

As you can see, the only answer is x = 0

 

[jburgswife30]

thank you very much