# Algebra and expressions

• Sep 30th 2007, 04:13 AM
sammyfox07
Algebra and expressions
hello i am not quite sure how to work out these questions could someone please explain to me what to do. Thanxx

Q1.
a. simplify 3a(squared)bx8a(cubed)b(squared)
b. Factorise completely x(squared)+xy-2x-2y

DOES ANYONE KNOW HOW TO WORK THIS OUT
Factorise completely x(squared)+xy-2x-2y
• Sep 30th 2007, 05:15 AM
topsquark
Quote:

Originally Posted by sammyfox07
hello i am not quite sure how to work out these questions could someone please explain to me what to do. Thanxx

Q1.
a. simplify 3a(squared)bx8a(cubed)b(squared)
b. Factorise completely x(squared)+xy-2x-2y

$\displaystyle 3a^2b \cdot 8a^3b^2 = (3 \cdot 8)(a^2 \cdot a^3)(b \cdot b^2) = 24a^5b^3$

Quote:

Originally Posted by sammyfox07
Q2. Factorise this expression into double brackets
a. x(squared)-2x-120

$\displaystyle x^2 - 2x - 120$

List all the factors of -120:
1, -120
2, -60
3, -40
4, -30
5, -24
6, -20
10, -12
etc

until you get to a pair that adds up to -2, which is the last pair that I listed.

So:
$\displaystyle x^2 - 2x - 120 = (x + 10)(x - 12)$

-Dan