W= l - 5 where w = width and l = length
area = 84 = l*w = l(l-5)
l(l-5) = 84
l^2 - 5l - 84 = 0
(l - 12)(l + 7) = 0
l = 12
length = 12 and width = 7
Isolate the x. Subtract 3x from both sides, and add 4 to both sides
-2x (-3x) - 4 (+4) < 3x (-3x) + 21 (+4)
-2x - 3x < 21 + 4
Simplify. Combine like terms
-5x < 25
Isolate the x. Divide -5 from both sides (remember to flip the sign).
-5x/-5 < 25/-5
x > 25/-5
x > -5
x > -5 is your answer
hope this helps
For the second problem the answer D, -9, -11
Answer:
Height: 3/2 inches
Length: 12 inches
Width: 4 inches
Step-by-step explanation:
Let x is the side length of the square
The height of the box by cutting squares off :x
- The new length of the cardboard = 15 -2x (because we cut from 4 corners)
- The new width of the cardboard = 7 -2x (because we cut from 4 corners)
The new volume of it is:
V = (15 -2x) (7 -2x) x
<=> V =
To maximum volume, we use the first derivative of the volume
<=> 
<=> 
<=> 2x -3 = 0 or 6x -35 = 0
<=> x = 3/2 or x = 35/6
To determine which value of x gives a maximum, we evaluate
= 24x -88
= 24(3/2) -88 = -52
= 24(35/6) -88 = 52
We choose x = 3/2 to have the maximum volume because the value of x that gives a negative value is maximum.
So the dimensions (in inches) of the box is:
Height: 3/2 inches
Length: 15-2(3/2) = 12 inches
Width: 7 - 2(3/2) = 4 inches
Answer:
C is the answer ,got it right on EDG 2020
Step-by-step explanation: