xy = -1
x + y = 2
x + y = -2
- x - x
y = -x - 2
xy = -1
x(-x + 2) = -1
x(-x) + x(2) = -1
-x² + 2x = -1
+ 1 + 1
-x² + 2x + 1 = 0
-1(x²) - 1(-2x) - 1(-1) = 0
-1(x² - 2x - 1) = 0
-1 -1
x² - 2x - 1 = 0
x = -(-2) ± √((-2)² - 4(1)(-1))
2(1)
x = 2 ± √(4 - 4(-1))
2
x = 2 ± √(4 + 4)
2
x = 2 ± √(8)
2
x = 2 ± 2√(2)
2
x = 1 ± √(2)
x + y = 2
(1 ± √(2)) + y = 2
- (1 ± √(2)) - (1 ± √(2))
y = 1 ± √(2)
(x, y) = (1 ± √(2), 1 ± √(2))
The numbers that multiply to -1 and add to 2 are 1 ± √(2).
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There is not enough evidence to support the administrator’s claim and the true mean is not significantly greater than 280.
<h3>What is a statistical hypothesis?</h3>
A hypothesis to test the given parameters requires that we determine if the mean score of the eighth graders is more than 283, thus:
The null hypothesis:

The alternative hypothesis:

From the population deviation, the Z test for the true mean can be computed as:


Z = 0.756
Note that, since we are carrying out a right-tailed test, the p-value for the test statistics is expressed as follows:
P(z > 0.756)
P = 0.225
Since the P-value is greater than the significance level at α = 0.14, we can conclude that there is not enough evidence to support the administrator’s claim and the true mean is not significantly greater than 280.
Learn more about hypothesis testing here:
brainly.com/question/16251072
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Accordinly to the details, i think that A could work.
Answer:
Step-by-step explanation:
f(x)=4+20+4
=28