Q. If f′(x)=2f(x) and f(1)=5, then f(3)=men for some integers m and n.What are m and n ?m=□n=□
Recognize Differential Equation: First, we recognize that f′(x)=2f(x) is a differential equation that describes exponential growth or decay. Since f(1)=5, we can use this initial condition to find the particular solution.
Guess Exponential Form: We can guess that f(x) is of the form Cekx because the derivative of an exponential function is proportional to the function itself. So, f′(x)=kCekx.
Substitute and Solve: Substituting f(x)=Cekx into the differential equation f′(x)=2f(x), we get kCekx=2Cekx. Dividing both sides by Cekx, we find that k=2.
Find Constant C: Now we know that f(x)=Ce2x. We can use the initial condition f(1)=5 to find C. Substituting x=1, we get f(1)=Ce2⋅1=5.
Calculate Particular Solution: Solving for C, we have Ce2=5. Dividing both sides by e2, we find C=e25.
Find f(3): So the particular solution to the differential equation is f(x)=(e25)e2x. Now we need to find f(3).
Find f(3): So the particular solution to the differential equation is f(x)=e25e2x. Now we need to find f(3).Substituting x=3 into f(x), we get f(3)=e25e2⋅3=e25e6.
Find f(3): So the particular solution to the differential equation is f(x)=e25e2x. Now we need to find f(3).Substituting x=3 into f(x), we get f(3)=e25e2⋅3=e25e6.Simplifying the expression, we have f(3)=5e4. This is the same as 5e4n where n=1, since 4⋅1=4.
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