A little Algebra, and we're home free!
We are given R = 20 and r2 = 75. We need to find r1.
The formula is 1/R = 1/r1 + 1/r2. Plug-in:
1/20 = 1/r1 + 1/75
1/20 - 1/75 = 1/r1
0.0366 = 1/r1
r1 = 1/0.03666
r1 = 27.272
Our answer is r1 = 27 ohms.
Answer:
60°
Step-by-step explanation:
x + 160° + 140° = 360°
x + 300° = 360°
x = 360° - 300°
x = 60°
Answer: its x = 3
Step-by-step explanation:
The maximum or minimum of a quadratic function occurs at
x
=
−
b
2
a
. If
a
is negative, the maximum value of the function is
f
(
−
b
2
a
)
. If
a
is positive, the minimum value of the function is
f
(
−
b
2
a
)
.
f
min
x
=
a
x
2
+
b
x
+
c
occurs at
x
=
−
b
2
a
Find the value of
x
equal to
−
b
2
a
.
x
=
−
b
2
a
Substitute in the values of
a
and
b
.
x
=
−
−
12
2
(
2
)
Remove parentheses.
x
=
−
−
12
2
(
2
)
Simplify
−
−
12
2
(
2
)
.
Tap for more steps...
x
=
3
The maximum or minimum of a quadratic function occurs at
x
=
−
b
2
a
. If
a
is negative, the maximum value of the function is
f
(
−
b
2
a
)
. If
a
is positive, the minimum value of the function is
f
(
−
b
2
a
)
.
f
min
x
=
a
x
2
+
b
x
+
c
occurs at
x
=
−
b
2
a
Find the value of
x
equal to
−
b
2
a
.
x
=
−
b
2
a
Substitute in the values of
a
and
b
.
x
=
−
−
12
2
(
2
)
Remove parentheses.
x
=
−
−
12
2
(
2
)
Simplify
−
−
12
2
(
2
)
.
Tap for more steps...
x
=
3
S=d/t ⇒d=s*t
s=speed
d=distance
t=time
The first train :
d=x
x=70 miles/h*t ⇒ x=70t (1)
The second train
d=360 miles - x
360 miles - x=80 miles/h*t ⇒360-x=80t ⇒ x=360-80t (2)
therefore, with the equations (1) and (2) we have a systeme of equations:
x=70t
x=360-80t
we can solve this system of equations by equalization method.
70t=360-80t
70t+80t=360
150t=360
t=360/150=2.4 (≈2 hour 24 minutes)
Answer: the first train meet with the second train in 2 hour 24 minutes.
