(X squared) = 15

[Mac_dw]

This one I missed also but I do not understand why???

Here is my origional work...
(X squared) = 15

(sqrt of X squared) = sqrt15

X = sqrt 15

 

[stapel]

You forgot the "±" on the right-hand side.

For instance, x² = 4, x² - 4 = 0, (x - 2)(x + 2) = 0, so x = 2 or x = -2. That is, x = ±2. The same holds here.

Eliz.

 

[Mac_dw]

Is it because I forgot the +/-???

 

[Mac_dw]

We must have crossed paths I see that it is. I did that on several problems. I should have stuck to using the quadratic equation and skipped the "short cut".

Thanx again

 

[Denis]

We must have crossed paths I see that it is. I did that on several problems. I should have stuck to using the quadratic equation and skipped the "short cut".

Hmm...well Mac, I don't think you need to waste precious time (on a test)
writing down all the stuff that stems from the quadratic...
general case: if a^2 = x, then a = +-sqrt(x) ; get my drift?

 

[Mac_dw]

Yeah...I see it.

Just not sure I'll remember to do it again?!? Long form guarantees it with the quadratic