The 15th arrangement will have both a blue and red ribbon
W= width
L= length= 2W-4
Perimeter= 70
FIND WIDTH:
P= 2(L + W)
P= 2L + 2W
substitute 2W-4 for L
70= 2(2W-4) + 2W
multiply 2 by all in parentheses
70= (2*2W) + (2*-4) + 2W
70= 4W - 8 + 2W
combine like terms
70= 6W - 8
add 8 to both sides
78= 6W
divide both sides by 6
13= W
FIND LENGTH:
substitute w=13 to find width
L= 2W-4
L= 2(13)-4
L= 26-4
L= 22
CHECK:
P= 2(L + W)
70= 2(22 + 13)
70= (2*22) + 2(13)
70= 44 + 26
70= 70
ANSWER:
length= 22 inches
width= 13 inches
Hope this helps! :)
An = a1 * r^(n-1)
-405 = -5*3^(n-1)
3^(n-1) = 81
3^4 = 81 so n-1 = 3 and n = 4
Sn = S4 = -5 (1 - 3^4) / ( 1 - 3) = 400 / -2 = -200 Answer
It takes 45 seconds. the easiest way to do these is to use a graphic calculator and replace the variables with x and y, for example, this equation would become -5x^2+30x, and if you don't have access to a graphing calculator, you can always use desmos online.