Answer:
2 real solutions
Step-by-step explanation:
y = -x^2 + 3x + 5
First find the the discriminant:
using b² - 4(a)(b)
(3)²- 4(-1)(5)
=9+20
=29
since the discriminant is more than 0, there are 2 real solutions
you place a cup of 200f coffee on a table in a room that is 67f and 10 minutes later it is 195f. approximately how long will it
be before the coffee is 180f
1 answer:
Newton's law of cooling says the rate of change of temperature is proportional to the difference between the object's temperature and the temperature of the environment.
Here, the object starts out at 200 °F, which is 133 °F greater than the environment temperature. 10 minutes later, the object is 195 °F, so is 128 °F greater than the environment. In other words, the temperature difference has decayed by a factor of 128/133 in 10 minutes.
The solution to the differential equation described by Newton's Law of Cooling can be written as the equation
T(t) = 67 + 133*(128/133)^(t/10)
where T is the object's temperature in °F and t is the time in minutes from when the object was placed in the 67 °F environment.
The equation
T(t) = 180
can be solved analytically, but it can be a bit easier to solve it graphically. A graphing calculator shows it takes 42.528 minutes for the temperature of the coffee to reach 180 °F.
Here, the object starts out at 200 °F, which is 133 °F greater than the environment temperature. 10 minutes later, the object is 195 °F, so is 128 °F greater than the environment. In other words, the temperature difference has decayed by a factor of 128/133 in 10 minutes.
The solution to the differential equation described by Newton's Law of Cooling can be written as the equation
T(t) = 67 + 133*(128/133)^(t/10)
where T is the object's temperature in °F and t is the time in minutes from when the object was placed in the 67 °F environment.
The equation
T(t) = 180
can be solved analytically, but it can be a bit easier to solve it graphically. A graphing calculator shows it takes 42.528 minutes for the temperature of the coffee to reach 180 °F.
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Answer:
Quadrant 4
Step-by-step explanation:
If the given angle was positive, then we go clockwise.
But it's negative so we go counterclockwise.
An alternative way of graphing
Quadrant 1 is 0-90°
Quadrant 2 is 90-180°
Quadrant 3 is 180-270°
Quadrant 4 is 270-360°
Subtract the given angle by 360 until no longer possible
750 - 360 = 390 390 - 360 = 30
Remember that this was originally a negative angle
Instead of going clockwise to quadrant 1, we go counterclockwise to quadrant 4, ending up at 330°
Answer:
B and F
Step-by-step explanation:
Given
x² + 4x + 4 = 12 ( subtract 4 from both sides )
x² + 4x = 8
Using the method of completing the square to solve for x
add ( half the coefficient of the x- term )² to both sides
x² + 2(2)x + 4 = 8 + 4, that is
(x + 2)² = 12 ( take the square root of both sides )
x + 2 = ± ( subtract 2 from both sides )
x = ± - 2
= ± 2 - 2
Hence
x = 2 - 2 → B
x = - 2 - 2 → F