Tom thinks of a number. He squares it, adds 3 times the original number and then subtracts 18. The result is 0. What two numbers could Tom have been thinking of?

Formulate the problem algebraically:x2+3x-18=0This is a factorisation problem. To find the solutions, factorise:-Factors of x2 are 1 and 1, so answer will take the form: (x +- ?)(x +- ?)=0-List pairs of factors of 18: (1,18), (2,9), (3,6). -When multiplied by factors of x2, find the factors of 18 that produce the x coeffcient: (3,6). -We now know factorised equation takes the form: (x +- 3)(x +- 6)=0-x coefficient is +3, so correct solution is +6 and -3 (6x+(-3x)=3x).-Factorised equation is (x-3)(x+6)=0-Equation holds when x=-6,3, so the two numbers Tom could have been thinking of are -6 and 3.

GH
Answered by George H. Maths tutor

3710 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

A shape consists of a quarter circle (radius r = 4cm) attached to a triangle (side length = 4cm and hypotenuse = 5cm). This shape is surrounded by a square (side length 8cm). If the shape is coloured in, what is the area in the square that is uncoloured?


In year 11, 3/7 of pupils go on holiday abroad in the summer break. Out of these, 1/3 go to France. Determine the ratio of pupils who go to France in summer to pupils who do not go to France in summer.


Prove that the square of an odd number is always 1 more than a multiple of 4


f(x)= 5 - x and g(x)= 3x + 7. Simplify f(2x) + g(x-1) (2018 past paper question)


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:

© 2026 by IXL Learning