To complete the square you compare your equation in the form x²+ bx + c = 0 to a similar equation of (x + b/2)² + c = 0. From expanding out the second equation we have x² + bx + (b/2)² + c = 0 we can see this differs from the first equation by the term (b/2)² so if we subtract (b/2)² we are back to the original equation. So the equation x²+ bx + c = 0 is equal to (x + b/2)² - (b/2)² + c = 0. So to solve this we can move the terms around to get (x + b/2)² = (b/2)² - c which can then be solved by taking the square root of both sides.

Find x: 4x + 7 = 27

Related Maths GCSE answers

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How to complete the square to find the value of x?

what is: a) 1/3 +1/4 ? b) 4/6 + 3/12?