Skip to main contentSkip to solution

If the area above x-axis, bounded by the curves y=3βxy = 3^{\beta x}, x=0x = 0 and x=3x = 3 is 26log⁡e3\frac{26}{\log_e 3}, then the value of β\beta is:

Solution

✅ Correct Option: 2

The curve is y=3βxy = 3^{\beta x}, bounded by x=0x = 0 and x=3x = 3, with area 26log⁡e3\frac{26}{\log_e 3}.

The area under the curve is given by:

Area=∫033βx dx\text{Area} = \int_0^3 3^{\beta x} \, dx


Using the integration formula ∫amx dx=amxmln⁡a\int a^{mx} \, dx = \frac{a^{mx}}{m \ln a}:

∫3βx dx=3βxβln⁡3\int 3^{\beta x} \, dx = \frac{3^{\beta x}}{\beta \ln 3}

where log⁡e3=ln⁡3\log_e 3 = \ln 3


Evaluating the definite integral:

∫033βx dx=[3βxβln⁡3]03\int_0^3 3^{\beta x} \, dx = \left[\frac{3^{\beta x}}{\beta \ln 3}\right]_0^3

=33ββln⁡3−30βln⁡3= \frac{3^{3\beta}}{\beta \ln 3} - \frac{3^{0}}{\beta \ln 3}

=33β−1βln⁡3= \frac{3^{3\beta} - 1}{\beta \ln 3}


Setting this equal to the given area:

33β−1βln⁡3=26ln⁡3\frac{3^{3\beta} - 1}{\beta \ln 3} = \frac{26}{\ln 3}

33β−1β=26\frac{3^{3\beta} - 1}{\beta} = 26

33β−1=26β3^{3\beta} - 1 = 26\beta

33β=26β+13^{3\beta} = 26\beta + 1


For β=1\beta = 1:

Left side: 33(1)=33=273^{3(1)} = 3^3 = 27

Right side: 26(1)+1=2726(1) + 1 = 27

Therefore, β=1\beta = 1

Keyboard Shortcuts

  • Left arrow: Previous question
  • Right arrow: Next question
  • S key: Jump to solution
  • Q key: Jump to question