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

3982 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

Factorise X^2 + 13x + 42; from this, please give the answer to X^2 + 13x + 42 = 0


y=2x+5, calculate x when y=11


(Economics A-level) Is the cross elasticity of demand for tea likely to be positive or negative following a rise in the price of milk? Explain your answer


Solve the simultaneous equations: 2x + y = 18, x - y =6.


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