Factorise and solve x^2 – 8x + 15 = 0

  • Google+ icon
  • LinkedIn icon
  • 685 views

This equation is of the form ax2 + bx + c = 0 (where a = 1, b = -8 and c = 15). To help solve it, find two numbers that add to give the value of b (the 'sum') and also when multiplied together give the same answer as a*c (the 'product'). 

For this equation, the sum = -8 and the product = 15.

Because the sum is negative and the product is positive we're looking for two negative numbers.

In this case they are -3 and -5, so the factorised equation would be: (x - 3)(x - 5) = 0.

In the factorised equation, the two bracket terms are multiplied together, so to solve the equation, make one of the brackets equal zero. 

The two 'roots' of the equation, i.e. the values of x that make the equation true, are x = 3 and x = 5.



 

Andrew B. GCSE Chemistry tutor, A Level Chemistry tutor, GCSE Maths t...

About the author

is an online GCSE Maths tutor who tutored with MyTutor studying at Oxford, Keble College University

Still stuck? Get one-to-one help from a personally interviewed subject specialist.

95% of our customers rate us

Browse tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok