530 views

### Factorise and solve x^2 – 8x + 15 = 0

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.

1 year ago

Answered by Andrew, who tutored GCSE Maths with MyTutor

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

#### 526 SUBJECT SPECIALISTS

£20 /hr

Xanthe W.

Degree: Biological Sciences with a Year in Industry/Research (Bachelors) - Imperial College London University

Subjects offered:Maths, Chemistry+ 1 more

Maths
Chemistry
Biology

£18 /hr

Seb C.

Degree: History and Politics (Bachelors) - York University

Subjects offered:Maths, History+ 1 more

Maths
History
English Literature

“Hi Everyone! I'm Seb and I am in first year studying History and Politics, both of which I am passionate about equally!”

MyTutor guarantee

£18 /hr

Eleanor J.

Degree: Natural Sciences in Maths and Physics (Masters) - Durham University

Subjects offered:Maths, Physics+ 1 more

Maths
Physics
Further Mathematics

“Study Maths and Physics at Durham Previous tutoring experience Enjoy helping students improve and enjoy the subjects Adaptable to different academic needs”

Andrew B.

Currently unavailable: until 01/09/2016

Degree: Chemistry (Masters) - Oxford, Keble College University

Subjects offered:Maths, Chemistry

Maths
Chemistry

MyTutor guarantee

### You may also like...

#### Posts by Andrew

Explain how electricity is conducted through a metal. To gain full marks your answer must include a description of the structure and bonding in a metal.

Factorise and solve x^2 – 8x + 15 = 0

Given that 5cos^2(x) - cos(x) = sin^2(x), find the possible values of cos(x) using a suitable quadratic equation.

Identify the dehydration product or products of a) ethanol, b) button-2-ol

#### Other GCSE Maths questions

Kelly is trying to work out the two values of w for which 3w - w^3 = 2 Her values are 1 and -1 Are her values correct? You must show your working.

Make X the subject of the equation (9x-7)/3 = 8y

Solve for X and Y: 2y + x = 7; 3y - x = 8

Rearrange the following, making c the subject: (3c + b)/2 = c + a

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