Answer:
124
Step-by-step explanation:
Using the product rule, we have
so that
The equation of the tangent line to <em>W(x)</em> at <em>x</em> = 7 has all the information we need to determine <em>m'</em> (7).
When <em>x</em> = 7, the tangent line intersects with the graph of <em>W(x)</em>, and
<em>y</em> = 4.5 + 2 (7 - 7) ==> <em>y</em> = 4.5
means that this intersection occurs at the point (7, 4.5), and this in turn means <em>W</em> (7) = 4.5.
The slope of this tangent line is 2, so <em>W'</em> (7) = 2.
Then
<u>M</u><u>e</u><u>t</u><u>h</u><u>o</u><u>d</u><u> </u><u>1</u><u> </u><u>:</u>
replace x and y by their value 1 and 3
3 = 4(1) - 1 = 4-1 = 3
2(1) + 3 = 2 + 3 = 5
correct
<u>M</u><u>e</u><u>t</u><u>h</u><u>o</u><u>d</u><u> </u><u>2</u><u> </u><u>:</u>
y = 4x - 1
2x + y = 5
y = 4x - 1
y = -2x + 5
y - y = 4x - 1 - ( -2x + 5 )
0 = 4x - 1 + 2x - 5
6x - 6 = 0
6x = 6
x = 6/6 = 1
y = 4x - 1
y = 4(1) - 1
y = 3
correct
Answer: 80 feet
Step-by-step explanation:
We can write these as fractions and do cross multiplication with the numerator being the height of the object while the denominator being the length of the shadow:
5 * 128 = 8x
640 = 8x
80 = x
Thus, the height of the lighthouse is 80 feet tall.
