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 ▸There are 12 counters in a bag. There is an equal number of red counters, yellow counters and blue counters in the bag. There are no other counters in the bag. 3 counters are taken from the bag. Work out the probability of taking 3 red counters.
I need help understanding simultaneous equations with more than two variables, can you please help?
1
Solve the following simultaneous equations. x^2 + 2y = 9, y = x + 3