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Byju's Answer
Standard VIII
Mathematics
Simplification of an Expression
fx=2 x3-15 x2...
Question
f
(
x
)
=
2
x
3
−
15
x
2
−
84
x
−
7
find
f
(
3
)
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Solution
f
(
x
)
=
2
x
3
−
15
x
2
−
84
x
−
7
f
(
3
)
=
2
(
81
)
−
15
(
9
)
−
84
(
3
)
−
7
⇒
162
−
135
−
252
−
7
=
−
232
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0
Similar questions
Q.
Find about maxima & minima
f
(
x
)
=
2
x
3
−
15
x
2
+
36
x
+
1
Q.
Find the critical points of the function
f
(
x
)
=
2
x
3
+
15
x
2
+
36
x
.
Q.
Find the intervals in which the following functions are increasing or decreasing.
(i) f(x) = 10 − 6x − 2x
2
(ii) f(x) = x
2
+ 2x − 5
(iii) f(x) = 6 − 9x − x
2
(iv) f(x) = 2x
3
− 12x
2
+ 18x + 15
(v) f(x) = 5 + 36x + 3x
2
− 2x
3
(vi) f(x) = 8 + 36x + 3x
2
− 2x
3
(vii) f(x) = 5x
3
− 15x
2
− 120x + 3
(viii) f(x) = x
3
− 6x
2
− 36x + 2
(ix) f(x) = 2x
3
− 15x
2
+ 36x + 1
(x) f(x) = 2x
3
+ 9x
2
+ 12x + 20
(xi) f(x) = 2x
3
− 9x
2
+ 12x − 5
(xii) f(x) = 6 + 12x + 3x
2
− 2x
3
(xiii) f(x) = 2x
3
− 24x + 107
(xiv) f(x) = −2x
3
− 9x
2
− 12x + 1
(xv) f(x) = (x − 1) (x − 2)
2
(xvi) f(x) = x
3
− 12x
2
+ 36x + 17
(xvii) f(x) = 2x
3
− 24x + 7
(xviii)
f
x
=
3
10
x
4
-
4
5
x
3
-
3
x
2
+
36
5
x
+
11
(xix) f(x) = x
4
− 4x
(xx)
f
x
=
x
4
4
+
2
3
x
3
-
5
2
x
2
-
6
x
+
7
(xxi) f(x) = x
4
− 4x
3
+ 4x
2
+ 15
(xxii) f(x) = 5x
3
/2
− 3x
5
/2
, x > 0
(xxiii) f(x) = x
8
+ 6x
2
(xxiv) f(x) = x
3
− 6x
2
+ 9x + 15
(xxv)
f
x
=
x
(
x
-
2
)
2