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If 
f^(')(x)=2f(x) and 
f(1)=5, then 
f(3)=me^(n) for some integers 
m and 
n.
What are 
m and 
n ?

{:[m=],[n=]:}

If f(x)=2f(x) f^{\prime}(x)=2 f(x) and f(1)=5 f(1)=5 , then f(3)=men f(3)=m e^{n} for some integers m m and n n .\newlineWhat are m m and n n ?\newlinem=n= \begin{array}{l} m= \square \\ n= \square \end{array}

Full solution

Q. If f(x)=2f(x) f^{\prime}(x)=2 f(x) and f(1)=5 f(1)=5 , then f(3)=men f(3)=m e^{n} for some integers m m and n n .\newlineWhat are m m and n n ?\newlinem=n= \begin{array}{l} m= \square \\ n= \square \end{array}
  1. Recognize Differential Equation: First, we recognize that f(x)=2f(x)f'(x) = 2f(x) is a differential equation that describes exponential growth or decay. Since f(1)=5f(1) = 5, we can use this initial condition to find the particular solution.
  2. Guess Exponential Form: We can guess that f(x)f(x) is of the form CekxCe^{kx} because the derivative of an exponential function is proportional to the function itself. So, f(x)=kCekxf'(x) = kCe^{kx}.
  3. Substitute and Solve: Substituting f(x)=Cekxf(x) = Ce^{kx} into the differential equation f(x)=2f(x)f'(x) = 2f(x), we get kCekx=2CekxkCe^{kx} = 2Ce^{kx}. Dividing both sides by CekxCe^{kx}, we find that k=2k = 2.
  4. Find Constant CC: Now we know that f(x)=Ce2xf(x) = Ce^{2x}. We can use the initial condition f(1)=5f(1) = 5 to find CC. Substituting x=1x = 1, we get f(1)=Ce21=5f(1) = Ce^{2\cdot 1} = 5.
  5. Calculate Particular Solution: Solving for CC, we have Ce2=5Ce^{2} = 5. Dividing both sides by e2e^{2}, we find C=5e2C = \frac{5}{e^{2}}.
  6. Find f(3)f(3): So the particular solution to the differential equation is f(x)=(5e2)e2xf(x) = \left(\frac{5}{e^{2}}\right)e^{2x}. Now we need to find f(3)f(3).
  7. Find f(3)f(3): So the particular solution to the differential equation is f(x)=5e2e2xf(x) = \frac{5}{e^{2}}e^{2x}. Now we need to find f(3)f(3).Substituting x=3x = 3 into f(x)f(x), we get f(3)=5e2e23=5e2e6f(3) = \frac{5}{e^{2}}e^{2\cdot 3} = \frac{5}{e^{2}}e^{6}.
  8. Find f(3)f(3): So the particular solution to the differential equation is f(x)=5e2e2xf(x) = \frac{5}{e^{2}}e^{2x}. Now we need to find f(3)f(3).Substituting x=3x = 3 into f(x)f(x), we get f(3)=5e2e23=5e2e6f(3) = \frac{5}{e^{2}}e^{2\cdot 3} = \frac{5}{e^{2}}e^{6}.Simplifying the expression, we have f(3)=5e4f(3) = 5e^{4}. This is the same as 5e4n5e^{4n} where n=1n = 1, since 41=44\cdot 1 = 4.

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