Algebra · Quadratic equations
Chapter 1 · 3
The idea
The quadratic formula
Where the formula comes from, how to substitute negative coefficients without sign disasters, and what the value under the square root says about how many solutions exist.
A full journey — read it, play with it, work it, then earn real exam marks. Everything stays on the timeline below.
In this lesson — start anywhere
Algebra · Quadratic equations
The quadratic formula
Where the formula comes from, how to substitute negative coefficients without sign disasters, and what the value under the square root says about how many solutions exist.
Why it works
One formula for every quadratic
Most quadratics don't factorise nicely — the roots of are not whole numbers, so no integer factor pair exists to hunt. The formula solves every quadratic in one move:It isn't magic: it is completing the square done once, in general, on — the answer to *"what does the square-completing recipe always give?"*, memorised so you never have to redo it.
Keep reading — free
The rest of the explanation, plus 2 worked examples you step through move by move.
Start freeTakes a minute — no card.