Melody

I really do not know what I am meant to be doing BUT

f(x)=-x+3; g(x)=x-4

g(x)=-f(x)-1

That is pretty tricky - drawing a map of your home state!         

$$\\12=\frac{20-4x}{3}\\
$mult both sides by 3$\\
36=20-4x\\
$subtract 20 from both sides$\\
16=-4x\\
$divide both sides by -4$\\
x=-4$$

check answer

right hand side (RHS)

= (20-4*-4)/3

= (20--16)/3

=(20+16)/3

=36/3

=12

= LHS  (Left hand side)

Astonomers use the doppler effect to calculate speed.

Sorry Chloe, I think you messed up a little.  

$$\\(3xy^2z^2)(-3x^3y^3z)^2\\\\
(3xy^2z^2)(9x^6y^6z^2)\\\\
27x^7y^8z^4\\\\$$

When you square root a negative number you get an imaginary number.

You probably don't know about those so you cannot square root a negative number - there are no REAL solutions.

Thanks Kitty :)

Not quite Chloe,

 $$\sqrt{9}=3$$

because 3*3=9

Really?  I didn't know that!

Thanks anon,

I'm not sure, is 4/9 a perfect square?  Perhaps someone would like to google that.