When should I use the quadratic formula?
If you're asked to solve a quadratic equation, you could factorise it, or you could use the quadratic formula. The quickest way is to factorise, but sometimes the numbers are too tricky to factorise, (if an exam question asks for the answer in decimal places, this is a good indication you will need this method) so in these situations we use the quadratic formula:
x= (-b+/-sqrt(b2-4ac))/2a
given the equation ax2+bx+c=0
You can then substitute the numbers from your equation into the formula, and you will get two values of x (remeber to do both + and - the square root) just like you would if you were to factorise the equation.
SM
Related Maths GCSE answers
All answers ▸Solve 5(x-6) < 20
I buy a car from a dealership for £3500. The car depreciates in value for every year I own it. What is the value of the car after I have owned it for 18 months if it depreciates at a rate of 5 percent?
What is the square root of 25?
Work out 2 3/4 x 1 1/2. Give your answer in terms of a mixed fraction in simplest form.