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Joint Entrance Examination
Mathematics
Area Under Curves
Question 228
Question 228 of 230
Medium
MCQ
If the area of the region
{
(
x
,
y
)
:
−
1
≤
x
≤
1
,
0
≤
y
≤
a
+
e
∣
x
∣
−
e
−
x
,
a
>
0
}
\left\{(x, y):-1 \leq x \leq 1,0 \leq y \leq \mathrm{a}+\mathrm{e}^{|x|}-\mathrm{e}^{-x}, \mathrm{a}>0\right\}
{
(
x
,
y
)
:
−
1
≤
x
≤
1
,
0
≤
y
≤
a
+
e
∣
x
∣
−
e
−
x
,
a
>
0
}
is
e
2
+
8
e
+
1
e
\frac{\mathrm{e}^2+8 \mathrm{e}+1}{\mathrm{e}}
e
e
2
+
8
e
+
1
, then the value of
a
a
a
is :
A
7
B
5
C
6
D
8
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Solutions · 1
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Official solution
\[
\begin{aligned} & \text { required area is } a+\int_\limits0^1\left(a+e^x-e^{-x}\right) d x \\ & a+\left[a+e^x+e^{-x}\right]_0^1 \\ & 2 a+e-1+e^{-1}-1=e+8+\frac{1}{e} \\ & 2 a=10 \Rightarrow a=5 \end{aligned}
\]
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