9514 1404 393
Answer:
3.61 seconds
Step-by-step explanation:
The bird starts 50 feet in the air, so will come down to a height of 40 feet after 3.61 seconds.
We want to solve h = 40.
40 = -16t^2 +55t +50
16t^2 -55t -10 = 0
t = (55 +√(55^2 -4(16)(-10)))/(2(16)) = (55 + √3665)/32 ≈ 3.61060
The bird will be 40 ft above the ground the first time after about 3.61 seconds.
9514 1404 393
Answer:
x = 7
Step-by-step explanation:
You solve a linear equation by putting the variable on one side of the equal sign and a constant on the other side. Here, variables and constants are on both sides of the equal sign, so you need to separate them.
The basic idea is that you add the opposite of any term you don't want. Whenever you perform any operation (like "add"), <em>you must do it to both sides of the equation</em>.
We observe that x-terms have coefficients of 10 and 9. We choose to add the opposite of 9x to both sides:
10 -9x -5 = 9x -9x +2
x -5 = 2 . . . . simplify
Now, we still have -5 on the left, where we don't want it. So, we add its opposite (+5) to both sides:
x -5 +5 = 2 +5
x = 7 . . . . simplify
The solution is x = 7.
_____
<em>Additional comment</em>
If we were to end up with an x-coefficient other than 1, we would divide both sides of the equation by that coefficient. This will leave the x-term with a coefficient of 1.
We know that
applying the law of cosines
a² = b²+ c²<span> – 2*b*c*cos(A)
</span>
in this problem
a=?
b=20
c=9
A=90°
so
a² = b²+ c² – 2*b*c*cos(A)
but
cos (A)=0
a² = b²+ c²-----> 20²+9²----> a²=400+81----> a²=481-----> a=√481
a=21.93-----> a=22
the answer is
22
