Mathematics multiplication, mathematics equation problems

1,5n=m-4, directly substituted into the following formula to obtain m -m(m-4)-4(m-4)=16,2, the original decomposition can obtain x + abxy + aby =x -4xy + 6y, the corresponding coefficient is equal, that is, a + b = -4, ab = 6, direct substitution of -4 3-2 6 = -24, 3 direct decomposition of the original formula to obtain 4a + a -4a + 4 = a +4 direct substitution to obtain 9

1， m2-5mn-20n=m(m-5n)-20n=4m-20n=4(m-5n)=16

2, (x+ay)(x+by)=x2+(a+b)xy+aby2=x2-4xy+6y2 If you correspond to it, you can see a+b=-4, ab=6, then 3(a+b)-2ab=-24

3, 4a+(a-2)2=4a+a2-4a+4=a2+4=9 is over, it should be very correct, give points, haha!

1. m=5n+4, substitution, 16

2. The left side of the equation x 2+(a+b)xy+aby 2, easy to obtain: a+b=-4, ab=6, substituting the algebraic formula, 24 is obtained

3. Algebraic simplification A 2+4, substituting A into 9. Here's what to say: whether a takes a positive or negative, it's all the same.

Surface area = height x bottom circumference, it can be known that the bottom perimeter = 4, so the bottom diameter should be 4cm(If you don't understand, please ask!)

Solution: Let the radius of the bottom surface of the cylinder be xcm, then the bottom diameter is 2xcm. Then according to the title:

2πx^2+2xπ*8=32π

Simplification: x 2 + 8x-16 = 0).

The solution is x1 = 4 2

4 ，x2=-4√2

4 (Off topic.) Drop off).

2x=2*（4√2

8 A: ...

Solution: Let the radius of the bottom surface be rThis can be obtained: 2 r*8 (side area) + 2*r (two base areas) = 32 ......The solution is: x=-4+ 2, so the diameter is -8+2 2

Hello!!!

The diameter of the bottom surface of the cylinder x;

Surface area = height x bottom circumference, solution: x=

Solution: Let's meet in x hours.

26x+17x=1075

43x=1075

x = 25 (hours).

A: Meet in 25 hours.

If the single digit is x, then the ten digit is x+5

So this number is 10 (x + 5) + x

The sum of you is x+x+5

So 10 (x+5) + x = 8 (x + x + 5) + 510x + 50 + x = 16x + 40 + 5

5x=5x=110(x+5)+x=61

A: The number is 61

Set the single digit to x

10(x+5)+x=8(x+5+x)+5

11x+50=16x+45

x=11+5=6

This number is 61

If the number of tens is x, then the number of single digits is x-5

10x+x-5=8（x+x-5）+5

11x-5=16x-35

x=6, so two digits are 61

Solution: Let the number in the single digit be a and the number in the ten digit be (a+5), then:

10（a+5)+a=[(a+5)+a)*8+511a+50=16a+45

5a=5a=1, that is, this two-digit number is 10 (a+5) + a=10 (1+5) + 1 = 61

Suppose the speed of the aircraft is x kilometers per hour.

then the downwind is X-24 and the upwind is X-24

2 hours 50 minutes = 17 6 hours.

So distance = 17 6 (x + 24) = 3 (x - 24) 17x + 406 = 18x - 432

x=8383(x-24)=2442

A: The speed of the aircraft is 838 kilometers per hour and the distance is 2442 kilometers.

Let the velocity of A be x and the velocity of B be y

then there is 2*(x+y)=20

A also walked for 2 hours when he returned to A.

2*(x-y)=4

x=6 km-h, y=4km-h.

Let the velocity of A be x and the velocity of B be y, 2(x+y)=20

2x=2y+4

The solution is x=6 km-h, y=4km-h.

Let the velocity of A be x and the velocity of B be yAccording to the question, we get: 2x+2y=20 2x-2y=4 Solve this system of equations, x=6 (kmh) y=4(kmh).

Solution: Let the speed of A be x kilometers and the speed of B be y kilometers per hour, then 2x+2y=20 (1) can be obtained from the distance between the two places ab mentioned in the question by 20 kilometers

From the other conditions given in the question, we get 2x-2y=4 (2).

1)-(2) can obtain 4y=16, and the solution y=4 is substituted into the equation (1), that is, 2x+2y=2x+8=20 is simplified, that is, 2x=12, and the solution is x=6

A: The first speed is 6 kmh, and the B speed is 4 kmh.

Let's assume that the whole workload is 1, A alone needs x days, and B needs y days, so their daily workload is 1 x and 1 y, respectively

Column equation: If two teams work together, it can be completed in 6 days: 1 (1 x+1 y) = 6 The number of days required for team B is a multiple of the number of days required for team A:

1) So x=10, y=15

2) The cooperation between the two teams can be completed in 6 days, and the cost is 10200 yuan, and the cooperation of A and B requires 10200 6=1700 yuan for one day.

Let's say A needs $x per day and B needs $y per day.

x+y=1700 x-y=300

So x=1000 y=700 A: 1000 10=10000 yuan B: 700 15=10500 yuan.

3) A's capital is less than B's, so A's choice is chosen.

1.It takes x days to set up a team.

1 (x+solution gives x=12 5.)

B: 18-5

Then you can forget about it.

The velocity of A. v

80/v+1/3-1)*

v = 40 then B's velocity.

The release date is x days.

1/x=1/（x+6）×2

1/x=2/（x+6）

x+6=2x

x=6 is tested to be the root of the equation.

I bought x kilograms of apples last Tuesday, 20 x-1) (1+50%) x=20+4x=4

Answer: If the speed of car A is kilometers and hours, then the speed of car B is kilometers and hours

Solve the equation: =40 km hour.

The speed of car B is kilometers per hour.

So the speed of car A is 40 kilometers per hour, and the speed of car B is 60 kilometers per hour.

Let A x (km h) and B y (km h).

A and B walk together for a time t=7 x

In that time, B has taken yt=7y x

During this time, B walked 1km more than A

Column: 7y x-1=7===>7y=8x---1)

1) (2) The solution is: x=, y=4

Method 2: A and B go through the whole process together, and the time taken is t=

During that time, B walked more than A.

Column: *****====>7y=8x---3)(2)(3) The solution is: x=,y=4