Showing posts with label MATHEMATICS NOTE. Show all posts
Showing posts with label MATHEMATICS NOTE. Show all posts
Thursday, 17 May 2012
FACTORISATIONS
Factorising is the reverse process of expansion.
When you factorise an expression, you write it as a product of two or more common factors.
Tip: You may have to find the Highest Common Factor (HCF) for the terms first in order to arrive at an answer.
Eg:
Factorise each of the following:
i) 3p + 6
ii) 8a2 - 6ab
iii) ab + ac + bd + cd
Solution:
i) 3p + 6 ( 3 is the HCF)
= 3(p + 2)
ii) 8a2 - 6ab (2a is the HCF)
= 2a(4a - 3b)
iii) ab + ac + bd + cd
= a(b + c) + d(b + c)
= (b + c) (a + d)
Factorisation is also done by using the difference of two squares:
(a2 - b2) = (a + b) (a - b)
or by your knowledge of perfect squares:
a2 + 2ab + b2 = (a + b)2
a2 - 2ab + b2 = (a - b)2
Eg:
Factorise 4p2 - 25q2
Solution:
4p2 - 25q2
= (2p + 5q) (2p - 5q)
*********************
Factorise the following:
a. 10a + 15 = 5(2a + 3)
b. 12ab - 18b2 = 6b(2a - 3b)
c. 4mn + 12mn2 = 4mn(1 + 3n)
d. 9x2 - 64y2 = (3x + 8y) (3x - 8y)
e. 4p2 - 100q2 = 4(p + 5q) (p - 5q)
f. 12a2 - 48b2 = 12(a + 2b) (a - 2b)
g. x2 + 6xy + 9y2 = (x + 3y)2
h. 3p2 + 6pq + 3q2 = 3(p + q)2
i. a2 + ab + 3a + 3b = (a + 3) (a + b)
j. mk - m2 + 4k - 4m = (m + 4) (k - m)
k. (a - 7)2 - 100 = (a + 3) (a - 17)
When you factorise an expression, you write it as a product of two or more common factors.
Tip: You may have to find the Highest Common Factor (HCF) for the terms first in order to arrive at an answer.
Eg:
Factorise each of the following:
i) 3p + 6
ii) 8a2 - 6ab
iii) ab + ac + bd + cd
Solution:
i) 3p + 6 ( 3 is the HCF)
= 3(p + 2)
ii) 8a2 - 6ab (2a is the HCF)
= 2a(4a - 3b)
iii) ab + ac + bd + cd
= a(b + c) + d(b + c)
= (b + c) (a + d)
Factorisation is also done by using the difference of two squares:
(a2 - b2) = (a + b) (a - b)
or by your knowledge of perfect squares:
a2 + 2ab + b2 = (a + b)2
a2 - 2ab + b2 = (a - b)2
Eg:
Factorise 4p2 - 25q2
Solution:
4p2 - 25q2
= (2p + 5q) (2p - 5q)
*********************
Factorise the following:
a. 10a + 15 = 5(2a + 3)
b. 12ab - 18b2 = 6b(2a - 3b)
c. 4mn + 12mn2 = 4mn(1 + 3n)
d. 9x2 - 64y2 = (3x + 8y) (3x - 8y)
e. 4p2 - 100q2 = 4(p + 5q) (p - 5q)
f. 12a2 - 48b2 = 12(a + 2b) (a - 2b)
g. x2 + 6xy + 9y2 = (x + 3y)2
h. 3p2 + 6pq + 3q2 = 3(p + q)2
i. a2 + ab + 3a + 3b = (a + 3) (a + b)
j. mk - m2 + 4k - 4m = (m + 4) (k - m)
k. (a - 7)2 - 100 = (a + 3) (a - 17)
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