P = 2L + 2w
Subtract 2L
from each side: P - 2L = 2w
Divide each side
by 2 : (P - 2L) / 2 = w
You could also write it as (P/2 - L) = w
Both answers are the same.
An=a1+d (n-1)
a1= 7
find d
Let's use a2
a2=1
1=7+d (2-1)
1=7+d
-7 both sides
d=-6
explicit formula is
an=7+-6 (n-1)
a14=?
a14=7-6 (14-1)
a14=7-6×13
a14=7-78
a14=-71
Method One
You could divide by 5 right away.
20/5 = - 3 + x
4 = - 3 + x Add 3 to both sides.
4 + 3 = x
x = 7
Method Two.
You could remove the brackets. This is slightly longer, but some questions can only be solved that way.
20 = 5(-3) + 5x
20 = -15 + 5x Add 15 to both sides
20 + 15 = 5x
35 = 5x Divide by 5
35/5 = x
7 = x
