X-9/3=56/x+4 solve for x

x = sqrt (273) / 2 - 1/2 or x = - 1/2 - sqrt (273) / 2

Step-by-step explanation:

Solve for x:

x - 3 = 56 / (x + 4)

Cross multiply:

(x - 3) (x + 4) = 56

Expand out terms of the left hand side:

x^2 + x - 12 = 56

Add 12 to both sides:

x^2 + x = 68

Add 1/4 to both sides:

x^2 + x + 1/4 = 273/4

Write the left hand side as a square:

(x + 1/2) ^2 = 273/4

Take the square root of both sides:

x + 1/2 = sqrt (273) / 2 or x + 1/2 = - sqrt (273) / 2

Subtract 1/2 from both sides:

x = sqrt (273) / 2 - 1/2 or x + 1/2 = - sqrt (273) / 2

Subtract 1/2 from both sides:

Answer: x = sqrt (273) / 2 - 1/2 or x = - 1/2 - sqrt (273) / 2