Okay, this is a simplified version of how to solve this complicated equation.
First add like terms but in this equation is not very efficient when solving.
So subtract the -2x squared from both sides and the equation should like mine
x⁴ + 4x³ + 12x + 45 = x ² -2x ² + 6x + 9
So keep the left side of the equation the same, but change the right like this because your adding the x squared.
-x² + 6x + 9
Now go back to the whole equation
x⁴ + 4x³ + 12x + 45 = -x² + 6x + 9
You can’t do anything on the left side of the equation do the same process with the other numbers like this:
x⁴ + 4x³ + 12x = -x² + 6x + 9 -45
You subtract the 45 from each side and it’s negative on the other side because you subtracted it.
Now add the 9 and -45 = -36
Now the equation should look like this:
x⁴ + 4x³ + 12x = -x² + 6x -36
Subtract -12x from each side and the 12x on the left side of the equation is canceled out and is gone
The equation should look like this:
x⁴ + 4x³ + = -x² + 6x -36 -12x
Then add the 6x and -12x because they are like terms
So this is the final simplified version of the complex problem
x⁴ + 4x³ + = -x² + -36 -6x
You can’t add any other like terms to find the value of x because x and x² can’t be added together