Factorise the quadratic equation: x^2 + 5x + 6 = 0 and hence find the two solutions to the equation.

  1. Start by writing the equation out again: x2 + 5x + 6 = 0

  2. I do it by thinking which two numbers add together to = 5 and which same two numbers multiply to = 6. The answer to this is 2 and 3.

  3. So the next step is to write the eqaution down in factorised form (there is no need to do any other thinking about the numbers to go inside the brackets becuase the coefficient of x2 is 1).

  4. So we now have: (x + 2)(x + 3) = 0 - This is the answer to the first part of the question.

  5. To get the answer to the second part, one of the two brackets must = 0 (because if two numbers multiplied together = 0, one number must = 0).

  6. So either x + 2 = 0, in which case x = -2, or x + 3 = 0 in which case x = -3. This is the answer to the second part.

7.To check, substitute these number back into the original equation: (-2)2 + 5(-2) + 6 = 4 - 10 + 6 = 0 (correct) (-3)2 + 5(-3) + 6 = 9 - 15 + 6 = 0 (correct)

CJ

Related Maths GCSE answers

All answers ▸

What is a vector?


A game consists of 5 cups turned upside down, under one of the cups is a prize. 5 friend's pick a cup in turn and lifts it up, if they get the prize, they win , but if not, the cup is removed and the next friend picks. What position is it best to pick?


Henry invest £8000 in youtube at a compound interest rate of 2% per year. He wants to earn more than £500 interest. Work out the least time, in whole years, that this would take?


An amount of money was invested for 8 years. It earned compound interest at 2.5% per year. After 8 years the total value of the investment was £11,696.67. Work out the total interest earned.