Brainlag PlusRewrite x² + bx + c as (x + p)² + q to find turning points, exact solutions and minimum values.
Halve the x number
(x + 3)² = x² + 6x + 9.
So x² + 6x is (x + 3)² with 9 too many.
- x² + 6x + 2
- halve 6: (x + 3)² = x² + 6x + 9
- x² + 6x + 2 = (x + 3)² − 9 + 2
- = (x + 3)² − 7
The number in the bracket is always half the coefficient of x. Then take away its square and add the number term.
The rest of this lesson and its 7 practice questions are in Plus.
Screen 1 of 4, free to read.
- 7 exam-style questions, marked as you go, each with a worked solution
- The Graph Plotter beside every question
- Anything you get wrong is saved to your flashcards