F ( x ) = - ( x -20 ) ( x - 100 ) =
= - ( x² - 100 x - 20 x + 2000 )=
- x² + 120 x - 2000
The greatest profit is when ; f´( x ) = 0
f ´ ( x ) = - 2 x + 120 = 0
2 x = 120, x = 60
60 purchase orders will generate the greatest profit.
One day has 24 hours.
One hour has 60 minutes.
One day has 24 x 60 = 1440 minutes.
1 yard is 3 feet.
150 yards x 3 = 450 feet.
150 yards per minute = 450 feet per minute.
450 x 1440 = 648,000 feet per day.
The range of the function is all real number values of y except y = 0.
Ordered pairs in the graph includes (-4, -0.5), (-2, -1), (-1, -2), (1, 2)
Problem:
Solve
2
x
+
5
y
=
−
3
;
3
x
−
y
=
21
Steps:
I will try to solve your system of equations.
3
x
−
y
=
21
;
2
x
+
5
y
=
−
3
Step: Solve
3
x
−
y
=
21
for y:
3
x
−
y
+
−
3
x
=
21
+
−
3
x
(Add -3x to both sides)
−
y
=
−
3
x
+
21
−
y
−
1
=
−
3
x
+
21
−
1
(Divide both sides by -1)
y
=
3
x
−
21
Step: Substitute
3
x
−
21
for
y
in
2
x
+
5
y
=
−
3
:
2
x
+
5
y
=
−
3
2
x
+
5
(
3
x
−
21
)
=
−
3
17
x
−
105
=
−
3
(Simplify both sides of the equation)
17
x
−
105
+
105
=
−
3
+
105
(Add 105 to both sides)
17
x
=
102
17
x
17
=
102
17
(Divide both sides by 17)
x
=
6
Step: Substitute
6
for
x
in
y
=
3
x
−
21
:
y
=
3
x
−
21
y
=
(
3
)
(
6
)
−
21
y
=
−
3
(Simplify both sides of the equation)
Answer:
y
=
−
3
and
x
=
6
