Assuming you are trying to solve for x:
First, subtract color(red)(a) from each side of the equation to isolate the x term while keeping the equation balanced:
-color(red)(a) + a - 2x^2 = -color(red)(a) - 5
0 - 2x^2 = -a - 5
-2x^2 = -a - 5
Next, divide each side of the equation by color(red)(-2) to isolate x^2 while keeping the equation balanced:
(-2x^2)/color(red)(-2) = (-a - 5)/color(red)(-2)
(color(red)(cancel(color(black)(-2)))x^2)/cancel(color(red)(-2)) = (-a)/-2 + (-5)/-2
x^2 = a/2 + 5/2
x^2 = (a + 5)/2
Now, take the square root of each side of the equation to solve for x while keeping the equation balanced. Remember the square root of a number produces a positive and negative result:
sqrt(x^2) = +-sqrt((a + 5)/2)
x = +-sqrt((a + 5)/2)
