You want to isolate S. S is being multiplied by 3/4.
You need to multiply 3/4 by its reciprocal to get rid of the 3/4 on the left side.
The reciprocal of 3/4 is 4/3.
The rule with equations is that you are allowed to multiplied both sides of an equation by the same number. Multiply both sides of the equation by 4/3.
4 x^2 + 20 x + 25 = 7 Divide both sides by 4: x^2 + 5 x + 25/4 = 7/4 Write the left-hand side as a square: (x + 5/2)^2 = 7/4 Take the square root of both sides: x + 5/2 = sqrt(7)/2 or x + 5/2 = -sqrt(7)/2 Subtract 5/2 from both sides: x = sqrt(7)/2 - 5/2 or x + 5/2 = -sqrt(7)/2 Subtract 5/2 from both sides: Answer: x = sqrt(7)/2 - 5/2 or x = -5/2 - sqrt(7)/2
