MHB Making x the subject in two equations

[Ellie1]

how do you make x the subject in
$$y=2x^2 +3$$

how do you make x the subject in
$$y=\sqrt{x \over 3}$$

 

[evinda]

how do u make x the subject in
y=2x squared +3

(Wave)

$y= 2x^2+3 \Rightarrow 2x^2=y-3 \Rightarrow x^2=\frac{y-3}{2} \Rightarrow x= \pm \sqrt{\frac{y-3}{2}}$

Notice that it has to be $y-3 \geq 0 \Rightarrow y \geq 3$.

how do you make x the subject in
y=\sqrt{xover3

Give it a try? (Thinking)

 

[MarkFL]

Hello, Ellie and welcome to MHB! :D

I have moved your thread since our "Introductions" subforum is meant for folks to post a bit about themselves to let our community know a bit about you.

I have retitled your thread so that is briefly describes the nature of the questions being asked.

We also ask that when you post questions, you show what you have tried so our helpers can see where you are stuck or what you may be doing wrong, and this way we can offer better help.

I am thinking your first equation is:

$$y=2x^2+3$$

What do you think is the first thing we should do in an effort to solve for $x$?

 

[topsquark]

(Wave)

$y= 2x^2+3 \Rightarrow 2x^2=y-3 \Rightarrow x^2=\frac{y-3}{2} \Rightarrow x= \pm \sqrt{\frac{y-3}{2}}$

Notice that it has to be $y-3 \geq 0 \Rightarrow y \geq 3$.

Perhaps you had already noticed this, and I would agree that it is good to point out [math]y \geq 3[/math] anyway, but I should point out that this condition is satisfied by the given equation.

-Dan