Solve a math problem Help solve a math problem

5x+4y+2z=3(x+y+z)+(3x+y-z)-x=3*30+50-x=140-x.

Take x as a known number to get the equation:

y+z=30-x，--1

y-z=50-3x。--2

Solution: y=40-2x, z=x-10.

Because: x,y,z>=0,40-2x>=0,x-10>=0,x>=0.

10<=x<=20.

5x+4y+2z=140-x, the maximum is 140-10=130. The minimum is 140-20=120.

Multiply the first formula by two and add it to the second formula to get 5x+4y+z=110, then the minimum value of the original formula is 110

Multiply the first formula by three and add the first formula to get 6x+4y+2z=140, the original formula is equal to 140-x, then the maximum value is 140

Upstairs wrong. The two equations given can be seen as equations for two planes. Their intersection is a straight line.

Let's find this straight line first, which is represented by a parameter:

x+y+z=30

3x+y-z=50 => x=x;y=40-2x;z=x-10 (these three formulas form a linear equation in space, and the x to the right of the equal sign can be written as t, which is represented by a parameter).

Linear parametric equation: x=t; y=40-2t;z=t-10, and then x, y, and z are all greater than zero to obtain the range of values of the parameter variable t.

t>0;t<20;t>10

Then, the parametric equation is brought into 5x+4y+2z, and 5x+4y+2z=140-t is obtained

Then according to the range of the value of t, we know that the maximum value is 130 and the minimum value is 120, and the mistake on the floor is to assume that x z is at 0, when in fact x has no value at 0.

1) Let the side length of a square be x, x 2+((56-4x) 4) 2=100

x^2+(14-x)^2=100

x = 6 or 8 is divided into two sections, 24m and 32m.

2) The sum of the area of the two square vegetable plots = x 2+(14-x) 22x 2-28x+196

2(x-7)^2+98

When x=7, there is a minimum value of 98 m2

When x=0 there is a maximum value of 196m2

Because x>0, the sum of the area is less than 196 m2

Because the quadrilateral ABCD is a parallelogram, therefore, ab=cd, so CEDA is an isosceles trapezoid, so AC=AE, and because AB=AE, BC=ADSO: ABC EAD(SSS).

Since ae bisects dab, bae is also equal to 25, and according to the sum of the inner angles of the triangle is equal to 180, ab=ae, so abe= aeb=77,5

From the above, it can be seen that DCB is equal to 103, 5, then ace is equal to 51,75, so AED is equal to 180-25-51,75=93,25

I don't know if the numbers are right or not, you do the math.

85 degrees ae bisects the angle bad, so the angle bae = angle ead, because ab = ae, angle abe = angle aeb, because ad is parallel to bc, so the angle dae = aeb (the wrong angle within the parallelogram is equal), because the triangle abe is an equilateral triangle. That is, the angle EAB = EAD = 60 degrees, because the angle EAC = 25 degrees, so the angle CAD = 35 degrees, the angle EDA = 35 degrees (it proves that it should be), so the angle AOD = 110 degrees (let the intersection of AC and DE be O), the angle AOE = 70 degrees, 180-25-70 = 85 degrees, that is, the angle AED = 85 degrees, the answer is absolutely correct.

x1 and x2 are the two roots of the equation x-square-2+msquare-7=0.

x1+x2=-2(m-1)

x1*x2=m^2-7

And x1 square clear which Li + x2 square = 10

x1 2+x2 2=(x1+x2) 2-2x1*x2=4(m-1) 2-2m 2+14=10

The solution is m=2 and brought back.

Late answers. x1=-1

x2=3 so a,b coordinates to find out.

Because. x1+x2=-2(m-1) =2

x1*x2=m^2-7 =-3

y=ax square + bx + c = = ay = a(x + 1) (x-3) = a (x square + -2x-3) = a(x-1) 2-4a

Because. The vertex coordinates are -4=-4a

So. a=1

So y = (x+1) (x-3) = x 2-2x-3 and the coordinates of the intersection point c with the y axis are slow guess (0, -3).

According to Veda's theorem.

Yes. x1+x2=2(m-1)

x1*x2=m^2-7

x1^2+x2^2=(x1+x2)^2-2*x1*x2=10 …i.e. 4(m-1) 2-

2(m^2-7)=10

The solution brings in m=2 and x 2-2x+m 2-7=0

The two equations are 3&-1

x1 is less than x2

Therefore x1=-1

The coordinates of x2=3a and b are (-1,0) (3,0) respectively according to the parabolic properties.

When x = -b 2a = 1 (ab two midpoints).

y=-4 i.e. a+b+c=-4

Bringing the two-point coordinates of AB into the parabolic equation can be obtained.

a-b+c=0

9a+3b+c=0

Solve systems of equations. Debi Xun.

a=1 b=-2

c=-3 parabola.

y=x^-2x-3

c coordinates (1,-4).

x1 square + x2 square = (x1 + x2) square - 2x1x2 = 4 (m-1) square - 2 (m square - 7) Bi Wang = 10

The solution is m=2, so x1=-1, x2=3 (because x1 is smaller than hand beam x2) so a(-1,0)b(3.).，0）

Because m is the vertex, m(1,-4).

Substituting these three slag spike points into y=ax square + bx+c can obtain a=1,b=-2,c=-3, so y=xsquare-2x-3,c(0,-3).

(This problem needs to make an auxiliary line to transform the known conditions and connect them with the problem you want to prove) parallel relationship. A brief proof is as follows:

As EM intersects BC at the point M, then there is angle C=Angle EMB In the triangle ABE and triangle MBE, there is angle 1=Angle 2, and angle A = Angle EMB, so angle AEB = BEMExplain that EB is again the bisector of the angle AEM. then the quadrilateral aemb is a parallelogram.

So ae bmi.e. ad bc

So there is angle 4 = angle adf = angle DFC = angle 2

So be df

It's really troublesome to do math problems on this, hehe, I keep switching keyboards, I'm dizzy).

Parallel: According to the conditions you give, you can know that in the quadrilateral ABCD, the sum of the four angles is 360°, because a= c, 1= 2, 4= 5

So 2 1 + 2 4 + 2 a = 360°

i.e. 1+ 4+ a=180°

1+ a+ aeb=180°

So aeb= 4

So be df

According to the number of students who are not less than 100 times account for 96, the number of 90-100 can be known, and because the frequency of the first two groups and the talk beat is, the total number of people is 12;

Because from left to right.

The frequency ratio of groups 2, 3, and 4 is 4:17:15, so the frequency of 110-120 = (17 4), and the frequency of 120-130 is (15 4).

So the excellent rate =;

Didn't understand the next one!

Dad is reading a book, he has been reading this book for two days, he read 20% of the book on the first day, and 15 pages on the second day, the ratio of the number of pages he has read to the number of pages he has not read is 2:3, how many pages are there in this book?

75 pages.

The ratio of the number of pages seen but not read is 2:3, so the number of pages that have been read accounts for 2 (2+3)=40% of the whole book, so the usage rate corresponds, and the unit "1" is found

15 (40%-20%) = 75 (pages), i.e. 75 pages in total.

, which gives x=75, so the book has a total of 75 pages.

Because there is no time limit, the number of labor force is the largest in terms of the net output value of each production x enterprise.

Net output value = 700x + 1200 * (360-9x) 4 = 108000-2000x

The function is monotonically decreasing, so when the production of product A is 0, the net output value is the largest, so the number of products produced in B is 360 4=90.

0 for product A and 90 for product B.

Consider f(x)=x 2,x

-pi,pi]

Extending it to a function with a period of 2*pi is an even function.

Convert f(x) to a Fourier series (omitted).

f(x)=pi^2/3+4(-cos(x)+cos(2x)/4-cos(3x)/9+cos(4x)/16-..

The above equation allows x=pi to obtain.

1+1/4+1/9+1/16+1/25+..=pi^2/6

10--- side area: square centimeters.

Bottom area: square centimeters.

Confetti area: square centimeters.

17--- radius 10

Question 10 is solved, I'll come to question 17.

square centimeters).

Many people don't go to school and can't see your textbooks, so it's best to send up the questions.