# Algebra help

• Feb 3rd 2008, 11:57 PM
hair pulling mum
Algebra help
i have two algebra questions that my daughter needs to answer
Expand 5(n-1)

and
factorise 5x - 15

could some one please explain to me how to do this .. so i can help her with her homework

thnks
Tania
• Feb 4th 2008, 01:04 AM
Jhevon
Quote:

Originally Posted by hair pulling mum
i have two algebra questions that my daughter needs to answer
Expand 5(n-1)

when we want to expand brackets, we take each thing just outside the bracket and multiply each thing on the inside. so here we have a 5 on the outside, so we take it and multiply the n on the inside and then the -1 on the inside and just add the answers.

so, $5(n - 1) = 5*n + 5*(-1) = 5n - 5$

Quote:

factorise 5x - 15
here we want to do the opposite. we want to look for what is common among the terms and pull it out. here we see that 5 is common. since we can get 5 out of 5x to leave x, since 5x = 5*x and 5 out of 15 to leave 3, since 15 = 3*5

so, $5x - 15 = 5x - 5(3) = 5(x - 3)$

do you get it?