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the constant of variation or namely its slope will be
Answer:
f(r) = (x -1)(x -4+√7)(x -4-√7)
Step-by-step explanation:
The signs of the terms are + - + -. There are 3 changes in sign, so Descartes' rule of signs tells you there are 3 or 1 positive real roots.
The rational roots, if any, will be factors of 9, the constant term. The sum of coefficients is 1 -9 +17 -9 = 0, so you know that r=1 is one solution to f(r) = 0. That means (r -1) is a factor of the function.
Using polynomial long division, synthetic division (2nd attachment), or other means, you can find the remaining quadratic factor to be r^2 -8r +9. The roots of this can be found by various means, including completing the square:
r^2 -8r +9 = (r^2 -8r +16) +9 -16 = (r -4)^2 -7
This is zero when ...
(r -4)^2 = 7
r -4 = ±√7
r = 4±√7
Now, we know the zeros are {1, 4+√7, 4-√7), so we can write the linear factorization as ...
f(r) = (r -1)(r -4 -√7)(r -4 +√7)
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<em>Comment on the graph</em>
I like to find the roots of higher-degree polynomials using a graphing calculator. The red curve is the cubic. Its only rational root is r=1. By dividing the function by the known factor, we have a quadratic. The graphing calculator shows its vertex, so we know immediately what the vertex form of the quadratic factor is. The linear factors are easily found from that, as we show above. (This is the "other means" we used to find the quadratic roots.)
Answer:
OPTION C: y = 2x² + 1
Step-by-step explanation:
To identify the function substitute the values of 'x' and 'y' and compare LHS and RHS.
OPTION A: y = -(5x + 1)
When x = -2, y = 9
Therefore, LHS = 9
RHS = -(5(-2) + 1) = -(-10 + 1) = 9
So, LHS = RHS.
Now, we check for the second pair. i.e., (x, y) = (-1, 3)
LHS = 3
RHS = -(-5 + 1) = -(-4) = 4
LHS RHS
So, this option is eliminated.
OPTION B: y = - 4x + 1
Like OPTION A, substitute x = -2 and y = 9.
LHS = 9
RHS = - 4(-2) + 1 = 9
LHS = RHS
Now for the second pair: (-1, 3)
LHS = 3
RHS = -4(-1) + 1 = 4 + 1 = 5
We see LHS RHS.
So, this option is eliminated as well.
OPTION C: y = 2x² + 1
Substituting the first pair: (-2, 9)
LHS = 9
RHS = 2(4) + 1 = 9
So, LHS = RHS
Now For the second pair: (-1, 3)
We have LHS = 3
RHS = 2(1) + 1 = 3
LHS = RHS.
The third pair: (0, 1)
LHS = 1
RHS = 2(0) + 1 = 1
For the pair: (1, 3)
LHS = 3
RHS = 2(1) + 1 = 3
Again, LHS = RHS
For the pair: (2, 9)
LHS = 9
RHS = 2(4) + 1 = 9
Since, for all the pairs we have LHS and RHS equal, we con conclude that this is the correct representation of our function.
Similarly, substitute OPTION D. The option can be eliminated in the second pair itself.
So, the answer is OPTION C.