Rate = 10/2 = 5 trees per hour
150trees/5 trees per hour = 30 hours
the answer is D = 30 hours
Nineteen million, two hundred sixty-six thousand, four hundred twenty! :)
First we'll do two basic steps. Step 1 is to subtract 18 from both sides. After that, divide both sides by 2 to get x^2 all by itself. Let's do those two steps now
2x^2+18 = 10
2x^2+18-18 = 10-18 <<--- step 1
2x^2 = -8
(2x^2)/2 = -8/2 <<--- step 2
x^2 = -4
At this point, it should be fairly clear there are no solutions. How can we tell? By remembering that x^2 is never negative as long as x is real.
Using the rule that negative times negative is a positive value, it is impossible to square a real numbered value and get a negative result.
For example
2^2 = 2*2 = 4
8^2 = 8*8 = 64
(-10)^2 = (-10)*(-10) = 100
(-14)^2 = (-14)*(-14) = 196
No matter what value we pick, the result is positive. The only exception is that 0^2 = 0 is neither positive nor negative.
So x^2 = -4 has no real solutions. Taking the square root of both sides leads to
x^2 = -4
sqrt(x^2) = sqrt(-4)
|x| = sqrt(4)*sqrt(-1)
|x| = 2*i
x = 2i or x = -2i
which are complex non-real values
Use the quadratic formula to find:
x
=
1
±
√
85
5
Explanation:
5
x
2
−
10
x
−
12
is of the form
a
x
2
+
b
x
+
c
with
a
=
5
,
b
=
−
10
and
c
=
−
12
This has discriminant
Δ
given by the formula:
Δ
=
b
2
−
4
a
c
=
(
−
10
)
2
−
(
4
×
5
×
−
12
)
=
100
+
240
=
340
=
2
2
⋅
85
This is positive, but not a perfect square, so the quadratic equation has a pair of irrational roots, given by the quadratic formula:
x
=
−
b
±
√
b
2
−
4
a
c
2
a
=
−
b
±
√
Δ
2
a
=
10
±
√
340
10
=
10
±
2
√
85
10
=
1
±
√
85
5
