43 - 28 + (12/2)

To get 19 as the answer you change the /2 to /3. Too Easy!

square root of 2= 1 =8^x

'  It's best if you restrict yourself to one equals sign per equation, otherwise it's difficult to figure out what you could actually mean.

Maths always makes me peckish, so if you don't mind could you please spell it "Pie"?

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True, but usually in problems like this they mean solve for y=0.

I expect poster will indicate whether that's the case here. 

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(x-2)(x+3)-(x-2)(x+4)

You can see there are two terms and they each have a common factor (x-2), so

if we take out the common factor it becomes

(x-2) [x+3 - (x+4)]

Now it's just a matter of removing the brackets around x+4 when there is

a negative sign in front of it.

(x-2) [x+3-x-4)]

And this can be simplified finally to .....

this is left as an exercise for you to finish. 

$$\textcolor[rgb]{1,0,1}{K.E. = \frac {1}{2}\ m\ v^2}$$

Sorry 'bout the garish color! A finger fumble on my tablet brought on that, and then

I just couldn't get the red background to cancel. Fortunately, they were at least different shades!

3^x * 9^x

= 3^x * (3^2)^x

= 3^x * 3^(2x)

= 3^(x+2x)

= 3^(3x)

= 3^3^x

= 27^x

Let's do an easy check. Does 3^5 * 9^5 = 27^5 on your calculator?  yes

The equation tells you. You subtract a term to make it vanish from a particular side of the equation, usually as part of your manouvering to isolate a variable by itself. In the process of making it disappear from one side, you inevitably cause it to appear on the other side.

Just make sure you are even-handed, what you do to one side must also be done to the other. You can divide everything on one side by some number, as long as you divide all on the other side by that same number. (Just make sure you don't try to do any division by zero!)

>> what if it was d/dx( 2 + sin (30x))

= 30.cos(30x)  (Answer)