Express x^2-4x+9 in the form (x-p)^2+q where p and q are integers

The first step would be to expand the second equation:(x-p)^2+qx^2-px-px+p^2+q

this simplifies to x^2-2px+p^2+q

After this you examine the two equations and identify their similarities such as the x^2 term and the terms with have a single x in them.

From this you can equate the terms which have similar terms (see below)

-2px=-4x and p^2+q=9

Next determine which equation is solvable.

As -2px=-4x only has one variable is it solvable.

Solving this equations gives:

-2px=-4x

cancelling x

-2p=-4

divide both sides by -2

p=2 (save this)

Next use this solution to solve the second equation:

p^2+q=9

substitute p=2

2^2+q=94+q=9

q=5 (save this)

Finally substitute the values for p and q into the original equation

 (x-p)^2+q

 final answer: (x-2)^2+5

This can be checked by expanding it and ensuring that it does become x^2-4x+9.

MN
Answered by Mark N. Maths tutor

14940 Views

See similar Maths A Level tutors

Related Maths A Level answers

All answers ▸

Prove that (1-cos2x)/sin(2x) = tan(x) where x ≠ nπ/2


Can you give an example of using the chain rule for differentiation? Example: Let y=(6 + 2x + 2x^2)^3, find dy/dx.


Differentiate f(x) = x sin(x)


A 2.4 m long plank of mass 20kg has 2 pins, each 0.5 meters from each respective plank end. A person of mass 40kg stands on the plank 0.1m from one of the pins. Calculate the magnitude of reactions at the pins for this structure to be in equilibrium.


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