Maths GCSE question help????

Hi every one!

it was on a qustion paper so i thought it would be easier answer the question with the picture of the shape
there are 2 questions and need help with both
can you pls tell me step by step how to solve these :eek3:

here's the link
http://farm4.static.flickr.com/3530/4082943692_60c993889f_o.jpg

Many thanks

Reply 1

Potally_Tissed

Question 8: Split the shape into two rectangles. Find the area of each individually. The rest should be fairly obvious to you.

Question 9: You are finding the difference between n squared and n. Try a few numbers in n^2 - n and hopefully you will see why it can never be prime.

Reply 2

namedeprived

For the first split the area up into two rectangles.

For the second answer, consider the factorisation of

n^2-n

. Remembering that

n \geq 3,

and that a prime number only has factors 1 and itself, why is this example not prime?

Reply 3

zahir27

namedeprived

For the first split the area up into two rectangles.

For the second answer, consider the factorisation of

n^2-n

. Remembering that

n \geq 3,

and that a prime number only has factors 1 and itself, why is this example not prime?

so for the first one i would have to work out 2x+1 and x+1 so like this
(2x+1)(x+1) = 2x²+2x+2
x(x+5) - x²+5x :confused:

i dont get it

Reply 4

namedeprived

zahir27

so for the first one i would have to work out 2x+1 and x+1 so like this
(2x+1)(x+1) = 2x²+2x+2This part is right
x(x+5) - x²+5x :confused:

i dont get it

The first part is right. However look again at the area of the second rectangle. The length can't be x+5 as this would mean the two rectangles would overlap giving you too large a value.

The length of the second rectangle therefore has to be x+5-(x+1) = 4 so area of second rectangle = 4x.

Now add up the expressions for these two rectangles and make equal to the value 21. Then rearrange into the form given.