# Thread: help with algebra

1. ## help with algebra

I'm not quite sure how to answer this question could somebody help me please.

Q1 Write a formula for
a) the perimeter
b) the area.

part 2. If the area is 40cm (squared), show that 15x-45=0

Sorry i didn't make this message clear in my previous thread.

2. Originally Posted by sammyfox07
I'm not quite sure how to answer this question could somebody help me please.

Q1 Write a formula for
a) the perimeter
b) the area.

part 2. If the area is 40cm (squared), show that 15x-45=0

Sorry i didn't make this message clear in my previous thread.
(sigh) You should've just posted this back in your original thread, but since the diagram is here I'll do it here.

The perimeter is the distance around the rectangle. So
$P = 2l + 2w$
where $l = 3x - 1$ and $w = 5$.
So what is the perimeter?

The area of a rectangle is $A = lw$, and you know this is 40. So:
$(3x - 1) \cdot 5 = 40$

$15x - 5 = 40$

Thus
$15x - 45 = 0$

-Dan