Solve the inequality x2-x-12 < 0 +
2 answers:
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Answer:
- Part (a) Vertex = (-3, -1)
- Part (b) Vertex = (4, 5)
- Part (c) function 2; max value = 5
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Explanations:
Part (a)
In this case, the vertex is the highest point, so the vertex of function 1 is (-3, -1)
If the parabola was flipped so that it opened upward, instead of downward, then the vertex would be the lowest point.
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Part (b)
We could graph this function to see where the highest or lowest point is, but there's another way we could find the vertex using algebra.
The given equation is in the form y = ax^2 + bx + c where in this case
- a = -2
- b = 16
- c = -27
The a and b values are plugged into the formula below to get
h = -b/(2a)
h = -16/(2*(-2))
h = -16/(-4)
h = 4
This is the x coordinate the vertex since the vertex is (h,k)
To find k, we plug that value of h into the original function to find its corresponding y value.
y = -2x^2 + 16x - 27
y = -2(4)^2 + 16(4) - 27
y = -2(16) + 16(4) - 27
y = -32 + 64 - 27
y = 5
We found that h = 4 leads to k = 5. The vertex is (h,k) = (4, 5)
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Part (c)
We'll compare the y values of each vertex
- Function 1 has a vertex of (-3, 1)
- Function 2 has a vertex of (4, 5)
The vertex with the larger y value is the winner, so that would be function 2. This parabola reaches a higher peak compared to the other curve.
The max value here is y = 5. In other words, it's the maximum output the function can produce.
If you graphed functions 1 and 2 together on the same xy grid (see below), you'll see that the curve for function 2 reaches a higher peak.
All exercises involve the same concept, so I'll show you how to do the first, then you can apply the exact same logic to all the others.
The first thing you need to know is that, when a certain quantity multiplies a parenthesis, you can distribute that number to every element in the parenthesis. This means that
So, is multiplying the parenthesis involving
and
, and we distributed it:
multiplies both
and
in the final result.
Secondly, you have to know how to recognize like terms, because they are the only terms you can sum. Two terms can be summed if they have the same literal expression. So, for example, you cannot sum , and neither
exponents count.
But you can su, for example,
or
So, take for example exercise 9:
We distribute the 1.2 through the first parenthesis:
And you can distribute the negative sign through the second parenthesis (it counts as a -1 to distribute):
So, the expression becomes
Now sum like terms: