Q. Let g(x)=xe3x.What is the absolute minimum value of g ?Choose 1 answer:(A) −3e1(B) e33(C) −e31(D) g has no minimum value
Find Derivative: To find the absolute minimum value of the function g(x)=xe3x, we need to find the critical points by taking the derivative of g(x) and setting it equal to zero.Let's find the derivative g′(x).g′(x)=dxd[xe3x]Using the product rule, where (u∗v)′=u′v+uv′, let u=x and v=e3x.u′=dxd[x]=1v′=dxd[e3x]=3e3xNow apply the product rule.g′(x)=u′v+uv′g(x)0g(x)1
Set Equal to Zero: Now we set the derivative equal to zero to find the critical points.0=e3x+3xe3xFactor out e3x from both terms.0=e3x(1+3x)Since e3x is never zero, we can divide both sides by e3x to get:0=1+3xNow solve for x.−1=3xx = −31
Critical Point Analysis: We have found a critical point at x=−31. To determine if this is a minimum, we can use the second derivative test or analyze the behavior of the first derivative around the critical point. Let's use the second derivative test.Find the second derivative g′′(x).g′′(x)=dxd[g′(x)]=dxd[e3x+3xe3x]Using the product rule again for the second term, where u=3x and v=e3x, we get:u′=dxd[3x]=3v′=dxd[e3x]=3e3xNow apply the product rule.g′′(x)=dxd[e3x]+dxd[3xe3x]=3e3x+3e3x+3x⋅3e3xg′′(x)0g′′(x)1
Second Derivative Test: Now we evaluate the second derivative at the critical point x=−31.g′′(−31)=6e−1+9(−31)e−1=e6−e3=e6−3=e3Since e3 is positive, the second derivative is positive at x=−31, which means the function is concave up at this point, and thus x=−31 is a local minimum. Because the function g(x)=xe3x goes to negative infinity as x goes to negative infinity and to positive infinity as x goes to positive infinity, this local minimum is also the absolute minimum.
Evaluate Second Derivative: Now we need to find the value of g(x) at the critical point x=−31 to determine the absolute minimum value.g(−31)=(−31)e3(−31)=(−31)e−1=−(3e1) This corresponds to answer choice (A).
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