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Mathematical function of college entrance examination
(i) Derive and analyze the positive and negative intervals of derivative function.

f(x)=e^x(e^x-2a- 1)-(a+ 1)x

f'=e^x(e^x-2a- 1)+e^2x-(a+ 1)

=e^x(2e^x-2a- 1)-(a+ 1)=2(e^x)? -(2a+ 1)e^x-(a+ 1)

Taking e x as a variable is a quadratic equation with one variable.

δ=(2a+ 1)? +8(a+ 1)

=4a? +4a+ 1+8a+8

=4a? + 12a+9

=(2a+3)? ≥0

Root e x = [2a+ 1 (2a+3)]/4

e^x 1=[2a+ 1+(2a+3)]/4=a+ 1;

Ex2 = [2a+1-(2a+3)]/4 =-1/2 (impossible);

(1)a+ 1≤0, a≤- 1, f'(x)=0 has no solution, and f' (x) > 0; 0, which is an increasing function in all fields r.

(2)a & gt; -1, f'(x)=0 has roots, e x = a+ 1, x = ln (a+ 1),

X≥ln(a+ 1), increasing function; X & ltLn(a+ 1), subtraction function;

When x = ln (a+ 1) and e x = a+ 1, there is a minimum value.

(ii) Minimum value >; 0 will do.

A≤- 1, which is an increasing function in all fields r,

f(-∞)& gt; 0,

f(-∞)= 0-(a+ 1)(-∞)=(a+ 1)∞,a+ 1 & gt; 0, a>- 1, contradiction, no solution;

a & gt- 1,f(x)min = f(ln(a+ 1))=(a+ 1)(a+ 1-2a- 1)-(a+ 1)ln(a+ 1)

=-a(a+ 1)-(a+ 1)ln(a+ 1)

=-(a+ 1)(a+ln(a+ 1))& gt; 0

a+ln(a+ 1)& lt; 0,

h(a)=a+ln(a+ 1)

H' (a) =1+1(a+ 1) > 0, h(a) is an increasing function, and a+1

∴ The solution is a>0