Solve x^2 - 9 = 4x + 12

x2 - 9 = 4x + 12 x2 - 9 - 4x = 12 x2 - 9 - 4x -12 = 0 x2 - 4x -21 = 0 Factorise into form (x + ?)(x + ?) Factors of -21 are +7 and -3 or -7 and +3 (x + 7)(x - 3) = x2 + 7x - 3x -21 = x2 + 4x -21 which isn't what we want so it must be (x - 7)(x + 3)(x - 7)(x + 3) = 0 so x = 7 and x = -3

KP
Answered by Kira P. Maths tutor

3414 Views

See similar Maths GCSE tutors

Related Maths GCSE answers

All answers ▸

What is Pythagoras' Theorem and how do I use it?


A right-angled triangle has an angle of 30 degrees and its hypotenuse has a length of 9cm. Find the length of either of the triangle's other two sides.


Rectangle A has a length of 3y cm and a width of 2x cm. Rectangle B has a length of (y + 4)cm and a width of (x + 6)cm. Rectangle A has a perimeter of 94cm and Rectangle B has a perimeter of 56cm. Solve x and y and calculate the areas of each rectangle.


Find the values of x and y when 3x+4y=18 and 4x+2y=14


We're here to help

contact us iconContact usWhatsapp logoMessage us on Whatsapptelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences