Answer:
See picture:)
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Tìm cực trị của hàm số z(x,y)=x^{3}+y^{3}+3xy-30
1 answer:
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Answer:
the second option is the correct one
Step-by-step explanation:
The equation of a line in point- slope form is
y - b = m(x - a)
where m is the slope and (a, b) a point on the line
To calculate m use the slope formula
m = ( y₂ - y₁ ) / (x₂ - x₁ )
with (x₁, y₁ ) = (7, 5) and (x₂, y₂ ) = (- 4, - 1)
m = =
=
Use either of the 2 points as (a, b)
using (- 4, - 1), then
y- (- 1) = (x - (- 4)), that is
y + 1 = (x + 4)
After 85 minutes of calls, there are $27.25 left on the card.
<h3>What is the remaining credit after 85 minutes of calls?</h3>
A linear equation in slope-intercept form is:
y = a*x + b
Where a is the slope.
If the line passes through two points (x₁, y₁) and (x₂, y₂) the slope is:
In this case, we know that the line passes through the points (22, 36.7) and (52, 32,20)
(points of the form (time, dollars)).
So the slope is:
The linear equation is then:
y = -0.15*x + b
To find the value of b, we use the point (22. 36.7)
36.7 = -0.15*22 + b
36.7 + 0.15*22 = b = 40
Then the linear equation is:
y = -0.15*x +40
The amount remaining in the credit card after 85 minutes is given by evaluating the above equation in x = 85.
y = -0.15*85 + 40 = 27.25
This means that after 85 minutes of calls, there are $27.25 left on the card.
If you want to learn more about linear equations:
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