Melody

Put it in the calc like this

-(5 +1/2)+(6+ 3/4)- (4 +1/4)

compounds 12 times a year so r=0.052/12   n= 12*5=60       FV=8000

$$\\8000=PV(1+0.052/12)^{60}\\\\
\frac{8000}{(1+0.052/12)^{60}}=PV\\\\$$

There is no question here.

I think that some of your question is missing  

You did not need Wolfram|Alpha Tetration jsut sub your answer in and check it works.

-16=6(y-8)-2y        y=8

RHS=1(8-8)-2*8 = 0-2*8 = -16 = LHS   so it is definitely correct  

Use the calc on the home page

$$\\x+\frac{2}{4x^2}+2x-8\\\\
=\frac{1}{2x^2}+2x+x-8\\\\
=\frac{1}{2x^2}+3x-8\\\\$$

You question makes no sense!

$$\\(-2x^4-3x+5x^2-x)*(x-3)\\\\
=(x-3)(-2x^4-3x+5x^2-x)\\\\
$First simplify inside the brackets if you can$\\\\
=(x-3)(-2x^4+5x^2-x-3x)\\\\
=(x-3)(-2x^4+5x^2-4x)\\\\
=x(-2x^4+5x^2-4x)-3(-2x^4+5x^2-4x)\\\\
$now expand the brackets but be careful with the -3$\\\\
=x(-2x^4+5x^2-4x)+(-3)(-2x^4+5x^2-4x)\\\\$$

That is a good start - you see if you can finish it    

Here is a worthwhile video one factoring quadratics.