How to do the first question?

Answer: by f'(x) 0, i.e., lnx+1 0 solution to x1 e, then the monotonic increase interval of the original function is [1 e, + the subtraction interval is (0,1 e].

So the minimum value of the function f(x) on [1,3] = f(1)=0

From the meaning of the title, 2xlnx -x2+ax-3, then a 2lnx+x+3 x

If x [1 e,e] exists for the inequality 2f(x) -x 2+ax-3 to hold, only a is less than or equal to the minimum value of 2lnx+x+3 x.

Let h(x)=2lnx+x+3 x(x 0), then h(x)=2x+1-3x2=(x+3)(x-1) x 2

When x [1 e,1), h'(x) 0, h(x) monotonically decreasing;

When x (1,e], h'(x) 0, h(x) monotonically incrementing.

From h(1 e)=-2+1 e+3e, h(e)=2+e+3 e, h(1 e)-h(e)=2e-2 e-4 0, h(1 e) h(e)

Therefore, when x [1 e,e], the minimum value of h(x) is h(e)=2+e+3 e;

Therefore a 2+e+3 e

1.Let y mx+n x

When x=1, y=m+n=4

When x=2, y=2m+n 2=5

2- gets n=2

Substituting gives m=2

Therefore y=2x+2 x then x=4 y=17 2

2 Let the line y=x+b(b 0) and m+3 m=4 m=1or3

m=1, y=3 b=2

m=3,y=1 b=-2 y=x+2

k^2x^2-(8k^2+4)x+16k^2=0;

According to Veda's theorem: x1+x2=8+k2 4; x1x2=16;

So: y1+y2=k(x1-4)+k(x2-4)=k(x1+x2)-8k=4 k; (k≠0)

Thus: the midpoint of ap o(x1 2+2; y1 2) is the center of the circle;

radius r=|ap|/2=]1/2√[(x1-4)^2+y1^2] ;

perpendicular straight line x=m;

Through the chord length relation, it can be determined that (l 2) 2+(m-x1) 2=r 2; According to the problem, it can be known that the chord length can maintain a fixed value, and a special value method can be used for the convenience of calculation.

i.e., assuming k=1;

then there is: l 2 4=r 2-(m-x1) 2 is a fixed value;

l^2/4=12-4√5-20-4√5(m-6)-(m-6)^2;

Further arrangement: right =-m 2-(4 5-12)m+28+20 5;

constructor: f(x)=-x 2-(4 5-12)x+28+20 5; find the derivative and make the derivative 0; Then there is :l:

Add 15 to the first box, 7 to the second box, 11 to the third box, 8 to the fourth box, 14 to the fifth box, and 7 to the sixth box.

Writing or arguing about the center, therefore, can be extracted as a paragraph. For example, the first sentence of "Squirrel" "The squirrel is a beautiful little animal" can be used as the meaning of the first paragraph;

Find the side area of a section first:

5 2 cm².

100 knots. 2512xi00 = 251200 square centimeters.

8 dm 80 cm.

80 5 400 square centimeters 40 dm.

100 40 dm 4000 dm 400 m.

That's probably what happened.

You don't know if you ask you every day without answering, you don't know if you ask me, and I don't know.

Take the problem seriously and find the solution to the problem carefully.

The biggest takeaway is to explore on your own.

8 dm 80 cm.

2*cm. square centimeters = 2512 square decimeters.

Suffer, begging, seedlings.

Wilt, commissioner, shrunk.

Repeatedly, over and over again.

1x=yy=n, ask what is x? x is x is 2 = x is -1.

ca.Photoresistor is the stronger the light, the smaller the resistance, the smaller the total resistance, and the greater the current bThe resistance of the photoresistor becomes smaller, and the ratio of the internal resistance, bulb, and resistance is smaller, and the voltage is reduced.

Select: d

When the photoresistor is exposed to an increase in the intensity of illumination, the resistance value decreases, and the current flowing through r increases, so D is selected.