 Quadratics can be solved in different ways. We learned how to solve them by factorizing and by completing the square in these videos. We're now going to discover how to solve quadratics using the quadratic formula. Quadratics can't always be factorized, but the quadratic formula does always work. Factorizing is easier to do, so it's better to check for that first. However, if you can't factorize, then we can use the quadratic formula instead. If the question says giving your answer to three significant figures, or giving your answer to two decimal places, it means these quadratics cannot be factorized. So straight away look to use the quadratic formula. So let's have a look at how to use the quadratic formula to solve quadratics. Firstly, make sure your quadratic equals zero. Then A is the number in front of the x-squared, B is the number in front of the x, and C is the number on its own. Make sure you keep the sign in front of the numbers. And then we just substitute the values into the formula. Let's have a look at an example. A is positive two, B is negative three, and C is negative four. And so we just substitute these numbers into the formula. Minus minus three plus or minus the square root of negative three squared minus four multiplied by two, multiplied by negative four. All of that divided by two multiplied by two. Be very careful with the negatives. Use brackets to prevent mistakes. We can either type that straight into our calculator. So minus minus three plus everything for one answer. And then to get the second answer type in minus minus three minus everything. Or we can simplify it a bit further. Three plus or minus the square root of 41 all divided by four. And then type this into our calculator. From your calculator you should get x equals 2.35 and x equals minus 0.851. So you can choose to jump straight in and use your calculator here. Or you can simplify it a little bit further and then use your calculator. Either way just be really careful with negatives. So here are a few for you to do. Remember to use brackets to help with negatives. We know that we need to use a quadratic formula because it tells us to round our answer. For b make sure the quadratic equals zero before you start. Pause the video, work them out and click play when you're ready. How did you get on? If you made a mistake go back and check your negatives. This is usually where mistakes are made. So there we have solving quadratics using the quadratic formula. a, b and c are just the coefficients from the equation and we substitute these numbers straight into the formula. Take your time and just be careful with negatives.