Fourteen less than three fourths of a number is negative eight. Find the number
1 answer:
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<h3>Answer: 33.75 feet</h3>
In fraction form, this value is equal to 135/4
33.75 ft is equivalent to 33 ft, 9 inches.
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Explanation:
Refer to the diagram below.
The key point to start with is point H, which is the vertex of the parabola.
Recall that vertex form is
y = a(x-h)^2 + k
What we'll do is plug in the vertex (h,k) = (60,30) which is the location of point H. We'll also plug in (0,45) which is the y intercept, aka the location of point C.
So,
y = a(x-h)^2 + k
y = a(x-60)^2 + 30 .... plug in vertex
45 = a(0-60)^2 + 30 .... plug in y intercept coordinates
45 = a(-60)^2 + 30
45 = a(3600) + 30
45 = 3600a + 30
45-30 = 3600a
3600a = 15
a = 15/3600
a = 1/240
This then means:
y = a(x-h)^2 + k
y = (1/240)(x-60)^2 + 30
This is the equation of our parabola. Plug in x = 30 to determine the height of point K
y = (1/240)(x-60)^2 + 30
y = (1/240)(30-60)^2 + 30
y = (1/240)(-30)^2 + 30
y = (1/240)(900) + 30
y = 15/4 + 30
y = 15/4 + 120/4
y = 135/4
y = 33.75
Therefore, the height of the power line, when it is 30 feet away from one of the poles, is 33.75 feet. This is the y coordinate of point K.
Side note: 33.75 ft = 33 ft + 0.75 ft = 33 ft + 12*0.75 in = 33 ft + 9 inches
<h3>Answer: Largest value is a = 9</h3>
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Work Shown:
b = 5
(2b)^2 = (2*5)^2 = 100
So we want the expression a^2+3b to be less than (2b)^2 = 100
We need to solve a^2 + 3b < 100 which turns into
a^2 + 3b < 100
a^2 + 3(5) < 100
a^2 + 15 < 100
after substituting in b = 5.
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Let's isolate 'a'
a^2 + 15 < 100
a^2 < 100-15
a^2 < 85
a < sqrt(85)
a < 9.2195
'a' is an integer, so we round down to the nearest whole number to get
So the greatest integer possible for 'a' is a = 9.
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Check:
plug in a = 9 and b = 5
a^2 + 3b < 100
9^2 + 3(5) < 100
81 + 15 < 100
96 < 100 .... true statement
now try a = 10 and b = 5
a^2 + 3b < 100
10^2 + 3(5) < 100
100 + 15 < 100 ... you can probably already see the issue
115 < 100 ... this is false, so a = 10 doesn't work