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Chapter 12: Factorisation > Exercise 12.2

Exercise 12.2

1. Factorise the following expressions.

Instructions

(i) a2+8a+16
a2+8a+16 = a2 + ×× + =

Instructions

(ii) p2−10p+25
p2−10p+25 = = p2 - × × + =

Instructions

(iii) 25m2+30m+9
25m2+30m+9 = + × × + =

(iv) 49y2+84yz+36z2

Instructions

49y2+84yz+36z2

  • The above identity is in the form of the identity: where a and b are two integers.
  • Thus, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

Instructions

(v) 4x2−8x+4
4x2−8x+4 = - 2 × × 2 + 22 =

(vi) 121b2−88bc+16c2

Instructions

121b2−88bc+16c2

  • The above identity is in the form of the identity: where a and b are two integers.
  • Thus, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

(vii) l+m2−4lm

Instructions

l+m2−4lm

  • Expand the first term using the identity
  • Upon simplifying, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

(viii) a4+2a2b2+b4

Instructions

a4+2a2b2+b4

  • Upon simplifying using the identity, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

2. Factorise.

Instructions

(i) 4p2 – 9q2
4p2 – 9q2 = - =

(ii) 63a2−112b2

Instructions

63a2−112b2

  • Take out the common factor of which gives us the form: a2−b2
  • Upon simplifying using the identity, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

Instructions

(iii) 49x2−36
49x2−36 = - =

(iv) 16x5−144x3

Instructions

16x5−144x3

  • Take out the common factor of which gives us the form: a2−b2
  • Upon simplifying using the identity, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

(v) l+m2−l−m2

Instructions

l+m2−l−m2

  • Upon expanding and simplifying using the identity, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

Instructions

(vi) 9x2y2−16
9x2y2 – = - =

(vii) x2−2xy+y2−z2

Instructions

x2−2xy+y2−z2

  • Upon simplifying using the identities, the resulting factorised form becomes
  • So, we get the following
  • Which gives us the above factorised answer

(viii) 25a2−4b2+28bc−49c2

Instructions

25a2−4b2+28bc−49c2

  • We observe that the three terms are together form an identity.
  • Upon simplifying using the identities, the resulting factorised form becomes
  • So, we get the following
  • Further on
  • Which gives us the above factorised answer

3. Factorise the expressions.

Instructions

(i) ax2 + bx
ax2 + bx =

(ii) 7p2+21q2

Instructions

7p2+21q2

  • Upon simplifying using the identities, the resulting factorised form becomes
  • So, we get the following as the factorised answer, upon taking the common factor.

Instructions

(iii) 2x3+2xy2+2xz2
2x3+2xy2+2xz2 =
(iv) am2+bm2+bn2+an2
am2+bm2+bn2+an2 = + =

(v) (lm + l) + m + 1

Instructions

lm+l+m+1

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Further on
  • So, we get the following as the factorised answer

(vi) y(y + z) + 9(y + z)

Instructions

yy+z+9y+z

  • Upon simplifying using the identities, the resulting factorised form becomes
  • So, we get the following as the factorised answer

(vii) 5y2−20y−8z+2yz

Instructions

5y2−20y−8z+2yz

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Upon simplifying
  • We get the factorised answer

(viii) 10ab + 4a + 5b + 2

Instructions

10ab+4a+5b+2

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Upon simplifying
  • We get the factorised answer

Instructions

(ix) 6xy – 4y + 6 – 9x
6xy – 4y + 6 −9x = 6xy−9x−4y+6 = 3x2y−3 – 22y−3 =

4. Factorise.

Instructions

(i) a4−b4
a4 – b4 = -
= =
(ii) p4−81
p4−81 = - =
= p2−32p2+9 =

(iii) x4 – y+z4

Instructions

x4−y+z4

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Upon simplifying
  • Further expanding using identities
  • More over we get
  • We get the factorised answer

(iv) x4 – x−z4

Instructions

x4−x−z4

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Upon simplifying
  • Further expanding using identities
  • More over we get
  • We get the factorised answer

(v) a4 – 2a2b2 + b4

Instructions

a4−2a2b2+b4

  • Upon simplifying using the identities, the resulting factorised form becomes
  • Upon simplifying
  • Further expanding using identities
  • More over we get
  • We get the factorised answer

5. Factorise the following expressions.

Instructions

(i) p2+6p+8
p2+6p+8 = p2+ + 4p + 8
= + =
(ii) q2−10q+21
q2 – 10q + 21 = q2 –3q -7q + 21 = (q–3) – (q–3) =
(iii) p2+6p−16
p2+6p−16 = p2 –2p + – 16 = (p–2) + (p–2) =