Please help 20 points
1 answer:
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Answer:
x = - , x =
Step-by-step explanation:
The absolute value function always gives a positive value, however, the expression inside can be positive or negative, that is
- 3x + 16 = 18 or -(- 3x + 16) = 18
Solving
- 3x + 16 = 18 ( subtract 16 from both sides )
- 3x = 2 ( divide both sides by - 3 )
x = -
or
-(- 3x + 16) = 18
3x - 16 = 18 ( add 16 to both sides )
3x = 34 ( divide both sides by 3 )
x =
As a check
Substitute these values into the left side of the equation and if equal to the right side then they are the solutions.
| - 3(- ) + 16 | = | 2 + 16 | = | 18 | = 18 ← True
| - 3( ) + 16 | = | - 34 + 16 | = | - 18 | = 18 ← True
Thus x = - and x =
are the solutions
Answer:
26 ft square by 13 ft high
Step-by-step explanation:
The tank will have minimum surface area when opposite sides have the same total area as the square bottom. That is, their height is half their width. This makes the tank half a cube. Said cube would have a volume of ...
2·(8788 ft^3) = (26 ft)^3
The square bottom of the tank is 26 ft square, and its height is 13 ft.
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<em>Solution using derivatives</em>
If x is the side length of the square bottom, the height is 8788/x^2 and the area is ...
x^2 + 4x(8788/x^2) = x^2 +35152/x
The derivative of this is zero when area is minimized:
2x -35152/x^2 = 0
x^3 = 17576 = 26^3 . . . . . multiply by x^2/2, add 17576
x = 26
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As the attached graph shows, a graphing calculator can also provide the solution.
