Factorise the expression: 2x^2 + 17x + 21

There are several ways to factorise this quadratic expression, but the best way in my opinon is:

  1. Take the constant in front of the x^2 and multiply it by the standalone constant (i.e. multiply 2 by 21, which gives 42). The constant in front of x is 17. This tells us that we need to find 2 numbers whose product is 42 and sum is 17.

  2. After trail and error, we know that these two numbers will be 14 and 3. Hence, the middle term (17x) will be split into these two terms (i.e. 13x and 4x), giving us 2x^2 + 14x + 3x + 21 . 

  3. Factorising these individually gives us: 2x(x+7) + 3(x+7) and final answer comes to (2x + 3) ( x + 7) 

TM
Answered by Tushar M. Maths tutor

8331 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Expand and simplify 3(m + 4) – 2(4m + 1)


ABC is a triangle with sides of length AB, 12m and BC,14m. Angle ACB = 43 degrees. Find the area of the triangle.


How would you find the mean for the numbers 100, 230, 450, 120 and 250?


y = 2x + 5, Calculate x when y = 4


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

MyTutor is part of the IXL family of brands:

© 2025 by IXL Learning