What is the vertex of the function?
1 answer:
Answer:
(4, -25)
Step-by-step explanation:
One way to answer this is to put the equation into vertex form.
f(x)= x^2 -8x -9 . . . . . given
Add and subtract the square of half the x-coefficient:
f(x) = x^2 -8x +(-8/2)^2 -9 -(-8/2)^2
f(x) = x^2 -8x +16 -25
f(x) = (x -4)^2 -25
Comparing this to the vertex form of a quadratic:
f(x) = a(x -h)^2 +k
we find that (h, k) = (4, -25). This is the vertex.
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<em>Alternate solution</em>
The line of symmetry for ...
f(x) = ax^2 +bx +c
is given by x = -b/(2a). For your given quadratic that line is ...
x = -(-8)/(2(1)) = 4
Evaluating f(4) gives the y-coordinate:
f(4) = 4^2 -8·4 -9 = -25
The vertex is (x, y) = (4, -25).
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Notice that every pair of point (x, y) in the original picture, has become (-y, -x) in the transformed figure.
Let ABC be first transformed onto A"B"C" by a 90° clockwise rotation.
Notice that B(4, 1) is mapped onto B''(1, -4). So the rule mapping ABC to A"B"C" is (x, y)→(y, -x)
so we are very close to (-y, -x).
The transformation that maps (y, -x) to (-y, -x) is a reflection with respect to the y-axis. Notice that the 2. coordinate is same, but the first coordinates are opposite.
ANSWER:
"<span>a 90 clockwise rotation about the origin and a reflection over the y-axis</span>"
Let ABC be first transformed onto A"B"C" by a 90° clockwise rotation.
Notice that B(4, 1) is mapped onto B''(1, -4). So the rule mapping ABC to A"B"C" is (x, y)→(y, -x)
so we are very close to (-y, -x).
The transformation that maps (y, -x) to (-y, -x) is a reflection with respect to the y-axis. Notice that the 2. coordinate is same, but the first coordinates are opposite.
ANSWER:
"<span>a 90 clockwise rotation about the origin and a reflection over the y-axis</span>"
<h3>Answer:</h3>
- 8 pieces
- 3/8 foot
a) Let n represent the number of 1 7/8 ft pieces. Then we have ...
... 16 1/2 ft = n × (1 7/8 ft)
We can find n by dividing this equation by 1 7/8.
... (16 1/2)/(1 7/8) = n = (132/8)/(15/8) = 132/15
... n = 8 12/15 = 8 4/5
The integer number of pieces that can be cut is 8 pieces.
b) The length of the left-over piece is 4/5 of the full length of a piece, so is ...
... (4/5) × (15/8 ft) = 12/8 ft
We want to divide this into 4 equal lengths, so each of those lengths will be 1/4 of the length of the left-over:
... (1/4) × (12/8 ft) = 3/8 ft
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<em>Comment on arithmetic with fractions</em>
This problem is easier if you <em>convert the mixed numbers to improper fractions</em>. This is done by expressing the integer as a number of fractional parts, then adding the fraction part of the mixed number:
... a + b/c = (a×c/c) + b/c = (ac +b)/c
Division with fractions is taught a couple of different ways. One way you can do it is to "invert and multiply". That is, you multiply the numerator fraction by the reciprocal of the denominator fraction:
... (a/b)/(c/d) = (a/b)×(d/c)
Another way you can do the division is to express each of the numerator and denominator fractions over the same denominator. Then the quotient is the ratio of numerators.
... (a/c)/(b/c) = a/b
This is the method we used here. Effectively, we converted 16 1/2 to 16 4/8 then to (16×8 +4)/8 = 132/8. Then the numerator and denominator fractions both had denominators of 8, so (132/8)/(15/8) = 132/15. This fraction can be reduced by removing a factor of 3 from numerator and denominator to give ...
... 132/15 = 44/5 = 8 4/5