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Mathematics
Problem
If
I
=
∫
d
x
x
−
9
x
2
+
4
x
+
6
I = \int \frac{dx}{x - \sqrt{9x^2 + 4x + 6}}
I
=
∫
x
−
9
x
2
+
4
x
+
6
d
x
to evaluate
I
I
I
, one of the most proper substitution could be a.
9
x
2
+
4
x
+
6
=
u
±
3
x
\sqrt{9x^2 + 4x + 6} = u \pm 3x
9
x
2
+
4
x
+
6
=
u
±
3
x
b.
9
x
2
+
4
x
+
6
=
3
u
±
x
\sqrt{9x^2 + 4x + 6} = 3u \pm x
9
x
2
+
4
x
+
6
=
3
u
±
x
c.
x
=
1
t
x = \frac{1}{t}
x
=
t
1
d.
9
x
2
+
4
x
+
6
=
1
t
9x^2 + 4x + 6 = \frac{1}{t}
9
x
2
+
4
x
+
6
=
t
1
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