x^2 - 10x + 21 = 0
- First, factorise the quadratic equation.
- Find two numbers that multiply to give 21 and add to give 10. 7 and 3
- (x-7)(x-3)=0
- Now find the value x so that when these brackets are multiplied together the answer is 0.
- So either x=7 or x=3
- You can check the answer by substituting 7 and 3 into the equation.
BS
Related Maths GCSE answers
All answers ▸find the integral of 1/x
Draw the following inequality on a graph: x^2+4x+1<-2
Ed has 4 cards. There is a number on each card. Three of the numbers are 12, 6 and 15. The mean of the numbers is 10. What is the fourth number?
The are 10 coloured balls in a bag, 4 red, 3 green, 2 orange and 1 yellow. John picks out balls and replaces them one at a time. What is the probability that the first two he picks are red?