Answer:
the 4th one
Step-by-step explanation:
Answer:
r=2
Step-by-step explanation:
r + 8 r + 11 = 29
( 1 + 8 ) r + 11 = 29 9 r + 11 = 29
Now we can isolate and solve for r while always keeping the equation balanced: First, subtract 11 from each side of the equation:
9 r + 11 − 11 = 29 − 11
9 r + 0 = 18
9 r = 18
Now we can divide each side of the equation by 9 to get
r : 9 over 9 = 18 under 9
1 r = 2
r = 2
Answer:
l(l - 2) = 168
Step-by-step explanation:
Let w = width
Let l = length
Let A = area
w = l - 2
A = l * w
also, A = 168
equating the two values of A
l * w = 168
l * (l - 2) = 168
l^2 - 2l = 168
l(l - 2) = 168
Answer:
x = 10 - 10sqrt(3)/3
Approximately 4.2265 cm
Volume = 1539.6 cm³
Step-by-step explanation:
Let the height be x
V = (20 - 2x)(40 - 2x)x
V = (800 - 80x - 40x + 4x²)x
V = 4x³ - 120x² + 800x
dV/dx= 12x² - 240x + 800 = 0
3x² - 60x + 200 = 0
x = [60 +/- sqrt(60² - 4(3)(200))]/6
x = [30 +/- 10sqrt(3)]/3
x = 10 +/- 10sqrt(3)/3
Approximately,
15.7735 and 4.2265
d²V/dx² = 24x - 240
For max, d²V/dx² < 0
So, x = 4.2265
V = (20 - 2x)(40 - 2x)x
Plug in x = 10 - 10sqrt(3)/3
V = 1539.600718
