How to complete the square to find the value of x?
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.
AA
Related Maths GCSE answers
All answers ▸Solve the following equation for x: x^2 - 4x - 17 = 4
What's the difference between the mean, median and mode?
Given that 3cm and 4cm are the shorter sides of a right-angled triangle, find the length of the hypotenuse.
Prove that the square of an odd number is always 1 more than a multiple of 4