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
the answer is five point six five, 5.65
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Answer:
The answer to the question is C
