Find 3 consecutive even numbers where the product of the smaller two numbers is 40 less than the square of the largest number.

1 answer:

5 0

$3\ consecutive\ even\ numbers:\ 2x,2x+2,2x+4\\\\2x(2x+2)+40=(2x+4)^2\\\\
4x^2+4x+40=4x^2+16x+16\\\\
4x^2-4x^2+4x-16x=16-40\\\\-12x=-24\ \ |:(-12)\\\\x=\frac{24}{12}=2\\\\2x=2=4\\\\2x+2=6\\\\2x+4=8\\\\Numbers\ are\ 4,6,8.$

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Answer:

a) Depth changing rate of change is $0.24m/min$ , When the water is 6 meters deep

b) The width of the top of the water is changing at a rate of $0.17m/min$ , When the water is 6 meters deep

Step-by-step explanation:

As we can see in the attachment part II, there are similar triangles, so we have the following relation between them $\frac{3.5}{10} =\frac{a}{h}$ , then $a=0.35h$ .

a) As we have that volume is $V=\frac{1}{2} 2ahL=ahL$ , then $V=(0.35h^{2})L$ , so we can derivate it $\frac{dV}{dt}=2(0.35h)L\frac{dh}{dt}$ due to the chain rule, then we clean this expression for $\frac{dh}{dt}=\frac{1}{0.7hL}\frac{dV}{dt}$ and compute with the knowns $\frac{dh}{dt}=\frac{1}{0.7(6m)(20m)}2m^{3}/min=0.24m/min$ , is the depth changing rate of change when the water is 6 meters deep.

b) As the width of the top is $2a=0.7h$ , we can derivate it and obtain $\frac{da}{dt}=0.7\frac{dh}{dt} =0.7*0.24m/min=0.17m/min$ The width of the top of the water is changing, When the water is 6 meters deep at this rate