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Find the factors of 3 x 2 + 2 x - 1 .

  1. The quadratic is in the required form.

  2. ( x ) ( x )

    Write down a set of factors for a and c . The possible factors for a are: (1,3). The possible factors for c are: (-1,1) or (1,-1).

    Write down a set of options for the possible factors of the quadratic using the factors of a and c . Therefore, there are two possible options.

    Option 1 Option 2
    ( x - 1 ) ( 3 x + 1 ) ( x + 1 ) ( 3 x - 1 )
    3 x 2 - 2 x - 1 3 x 2 + 2 x - 1
  3. ( x + 1 ) ( 3 x - 1 ) = x ( 3 x - 1 ) + 1 ( 3 x - 1 ) = ( x ) ( 3 x ) + ( x ) ( - 1 ) + ( 1 ) ( 3 x ) + ( 1 ) ( - 1 ) = 3 x 2 - x + 3 x - 1 = x 2 + 2 x - 1 .
  4. The factors of 3 x 2 + 2 x - 1 are ( x + 1 ) and ( 3 x - 1 ) .

Factorising a trinomial

  1. Factorise the following:
    (a) x 2 + 8 x + 15 (b) x 2 + 10 x + 24 (c) x 2 + 9 x + 8
    (d) x 2 + 9 x + 14 (e) x 2 + 15 x + 36 (f) x 2 + 12 x + 36
  2. Factorise the following:
    1. x 2 - 2 x - 15
    2. x 2 + 2 x - 3
    3. x 2 + 2 x - 8
    4. x 2 + x - 20
    5. x 2 - x - 20

  3. Find the factors for the following trinomial expressions:
    1. 2 x 2 + 11 x + 5
    2. 3 x 2 + 19 x + 6
    3. 6 x 2 + 7 x + 2
    4. 12 x 2 + 8 x + 1
    5. 8 x 2 + 6 x + 1

  4. Find the factors for the following trinomials:
    1. 3 x 2 + 17 x - 6
    2. 7 x 2 - 6 x - 1
    3. 8 x 2 - 6 x + 1
    4. 2 x 2 - 5 x - 3

Factorisation by grouping

One other method of factorisation involves the use of common factors. We know that the factors of 3 x + 3 are 3 and ( x + 1 ) . Similarly, the factors of 2 x 2 + 2 x are 2 x and ( x + 1 ) . Therefore, if we have an expression:

2 x 2 + 2 x + 3 x + 3

then we can factorise as:

2 x ( x + 1 ) + 3 ( x + 1 ) .

You can see that there is another common factor: x + 1 . Therefore, we can now write:

( x + 1 ) ( 2 x + 3 ) .

We get this by taking out the x + 1 and seeing what is left over. We have a + 2 x from the first term and a + 3 from the second term. This is called factorisation by grouping .

Find the factors of 7 x + 14 y + b x + 2 b y by grouping

  1. There are no factors that are common to all terms.

  2. 7 is a common factor of the first two terms and b is a common factor of the second two terms.

  3. 7 x + 14 y + b x + 2 b y = 7 ( x + 2 y ) + b ( x + 2 y )
  4. x + 2 y is a common factor.

  5. 7 ( x + 2 y ) + b ( x + 2 y ) = ( x + 2 y ) ( 7 + b )
  6. The factors of 7 x + 14 y + b x + 2 b y are ( 7 + b ) and ( x + 2 y ) .

Khan academy video on factorising a trinomial by grouping.

Factorisation by grouping

  1. Factorise by grouping: 6 x + a + 2 a x + 3
  2. Factorise by grouping: x 2 - 6 x + 5 x - 30
  3. Factorise by grouping: 5 x + 10 y - a x - 2 a y
  4. Factorise by grouping: a 2 - 2 a - a x + 2 x
  5. Factorise by grouping: 5 x y - 3 y + 10 x - 6

Simplification of fractions

In some cases of simplifying an algebraic expression, the expression will be a fraction. For example,

x 2 + 3 x x + 3

has a quadratic in the numerator and a binomial in the denominator. You can apply the different factorisation methods to simplify the expression.

x 2 + 3 x x + 3 = x ( x + 3 ) x + 3 = x provided x - 3

If x were 3 then the denominator, x - 3 , would be 0 and the fraction undefined.

Simplify: 2 x - b + x - a b a x 2 - a b x

  1. Use grouping for numerator and common factor for denominator in this example.

    = ( a x - a b ) + ( x - b ) a x 2 - a b x = a ( x - b ) + ( x - b ) a x ( x - b ) = ( x - b ) ( a + 1 ) a x ( x - b )
  2. The simplified answer is:

    = a + 1 a x

Simplify: x 2 - x - 2 x 2 - 4 ÷ x 2 + x x 2 + 2 x

  1. = ( x + 1 ) ( x - 2 ) ( x + 2 ) ( x - 2 ) ÷ x ( x + 1 ) x ( x + 2 )
  2. = ( x + 1 ) ( x - 2 ) ( x + 2 ) ( x - 2 ) × x ( x + 2 ) x ( x + 1 )
  3. The simplified answer is

    = 1

Simplification of fractions

  1. Simplify:
    (a) 3 a 15 (b) 2 a + 10 4
    (c) 5 a + 20 a + 4 (d) a 2 - 4 a a - 4
    (e) 3 a 2 - 9 a 2 a - 6 (f) 9 a + 27 9 a + 18
    (g) 6 a b + 2 a 2 b (h) 16 x 2 y - 8 x y 12 x - 6
    (i) 4 x y p - 8 x p 12 x y (j) 3 a + 9 14 ÷ 7 a + 21 a + 3
    (k) a 2 - 5 a 2 a + 10 ÷ 3 a + 15 4 a (l) 3 x p + 4 p 8 p ÷ 12 p 2 3 x + 4
    (m) 16 2 x p + 4 x ÷ 6 x 2 + 8 x 12 (n) 24 a - 8 12 ÷ 9 a - 3 6
    (o) a 2 + 2 a 5 ÷ 2 a + 4 20 (p) p 2 + p q 7 p ÷ 8 p + 8 q 21 q
    (q) 5 a b - 15 b 4 a - 12 ÷ 6 b 2 a + b (r) f 2 a - f a 2 f - a
  2. Simplify: x 2 - 1 3 × 1 x - 1 - 1 2

Summary

  • Product of two binomials
  • Factorising
  • Distributive law
  • Sum and difference of cubes
  • Factorising quadratics
  • Factorising by grouping
  • Simplifying fractions

End of chapter exercises

  1. Factorise:
    (a) a 2 - 9 (b) m 2 - 36 (c) 9 b 2 - 81
    (d) 16 b 6 - 25 a 2 (e) m 2 - ( 1 / 9 ) (f) 5 - 5 a 2 b 6
    (g) 16 b a 4 - 81 b (h) a 2 - 10 a + 25 (i) 16 b 2 + 56 b + 49
    (j) 2 a 2 - 12 a b + 18 b 2 (k) - 4 b 2 - 144 b 8 + 48 b 5

  2. Show that ( 2 x - 1 ) 2 - ( x - 3 ) 2 can be simplified to ( x + 2 ) ( 3 x - 4 )

  3. What must be added to x 2 - x + 4 to make it equal to ( x + 2 ) 2

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
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Source:  OpenStax, Maths test. OpenStax CNX. Feb 09, 2011 Download for free at http://cnx.org/content/col11236/1.2
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