The result of factoring polynomial 2mx2-4mxy + 2my2 is______ ．

The result of factoring polynomial 2mx2-4mxy + 2my2 is______ ．

2mx2-4mxy+2my2，=2m（x2-2xy+y2），=2m（x-y）2．

Several math problems in grade one of junior high school
1. A marching column moves at the speed of 8 km / h, and the correspondent at the end of the column rushes to the front of the column at the speed of 12 km / h to send a document. After the document is sent to the end of the column, it will take 14.4 minutes
2. The basic price of household electricity in a city is 0.4 yuan per kilowatt hour. If the monthly electricity consumption exceeds 48 kilowatt hours, 70% of the basic electricity price will be charged for the excess. If the average electricity charge in June is 0.36 yuan per kilowatt hour, how many kilowatt hours does the household share and how much electricity charge should be paid in June?
3. A plane flies between the two cities with a wind speed of 24 km / h. It takes 2 hours and 50 minutes to fly along the wind and 3 hours to fly against the wind. Calculate the speed of the plane when there is no wind and the distance between the two cities

The team is x kilometers long
14.4 minutes = 0.24 hours
x/(12-8)+x/(12+8)=0.24
25x+5x=24
30x=24
x=0.8
(2) Set common power X degree
0.4*48+[x-48]*0.4*0.7=0.36x
x=72
That is to say, the shared power is 72 degrees, and the fee payable is 72 * 0.36 = 25.92 yuan
three
Let the speed of windless flight be V km / h, and the distance between the two cities be s km
2 hours 50 minutes = 17 / 6 hours
(v+24)*17/6=s
(v-24)*3=s
v=840
S = (v-24) * 3 = (840-24) * 3 = 2448 km

Is the sentence "positive rational numbers and negative rational numbers make up all rational numbers"?

No. rational numbers are divided into positive rational numbers, zero rational numbers and negative rational numbers

A rectangular tin water tank, the bottom is a square, the water tank is 5 decimeters high, its side area is 80 square decimeters, the water tank
How much water can be made? (not counting the thickness, the weight of water per cubic decimeter is 1kg. Step by step formula)

Magnificent 999,
Bottom edge length: 80 △ 5 △ 4 = 4 (decimeter)
Can hold water: 4 × 4 × 5 × 1 = 80 (kg)

If △ ABC is known, extend BC to d so that CD = BC. Take the midpoint F of AB and connect FD to AC at point E. (1) find the value of aeac; (2) if AB = a, FB = EC, find the length of AC

(1) F is the midpoint of AB, M is the midpoint of BC, FM = 12ac. ∵ FM ∥ AC, ∵ CED = ∥ MFD, ∥ ECD = ∥ FMD. ∥ ECD. ∥ DCDM = ECFM = 23. ∥ EC = 23fm = 23 × 12ac = 13ac. ∥ aeac − ECAC = AC − 13acac = 23

Given that a (4,0), B (2,2) is a point in the ellipse with a 5 and B 3, and M is the upper moving point of the ellipse, what is the minimum absolute value of Ma + MB?

a=5 b=3
So C = 4 (a is the focus)
E = C / a = 4 / 5, x = 25 / 4
The distance from m to the guide line mm ~ = 25 / 4-x
When B M is three points and one line, the minimum absolute value of Ma + MB = MB + Em ~ m = m ~ b = 25 / 4-2 = 17 / 4

As shown in the figure, rectangular paper ABCD, e and F are the points on BC and AC respectively, AE = CE. If the paper is folded along AE, point B just falls on point F
Is AF equal to CF? Why?

AF is equal to CF for the following reasons:
Fold the paper along the AE
Then triangle Abe and triangle AEF are congruent
Thus, AFE = Abe = 90 degrees
In right triangle AEF and right triangle EFC
Known AE = CE
EF is the common side
≌ right triangle AEF ≌ right triangle EFC (hypotenuse, right side)
So AF = CF (the corresponding sides of congruent triangles are equal)

Let the two roots of the equation 4x & # 178; - 7x-3 = 0 be: x1, x2. Solve the equation and find the values of the following expressions
x1²+x2² （x1-3）（x2-3）

The two roots of 4x & # 178; - 7x-3 = 0 are: x1, x2. According to Weida's theorem: X1 + x2 = 7 / 4x1x2 = - 3 / 4 (1) X1 & # 178; + x2 & # 178; = (x1 + x2) &# 178; - 2x1x2 = (7 / 4) &# 178; + 3 / 2 = 49 / 16 + 24 / 16 = 73 / 16 (2) (x1-3) (x2-3) = x1x2-3 (x1 + x2) + 9 = - 3 / 4-21 / 4 + 9 = - 6 + 9 = 3

As shown in the figure: AE is the bisector of ∠ BAC in square ABCD, AE intersects BD and BC at f and e respectively, AC and BD intersect at O, verification: of = 12ce

It is proved that: take the midpoint P of AE, connect OP, ∵ point O is the midpoint of AC, ∵ OP is the median line of △ ace, ∵ OP = 12ce, Op ∥ ad, ∵ OPF = ∵ ead = ∵ EAC + ∵ CAD = ∵ EAC + 45 ° and ∵ ONP = ∵ abd + ∵ BAE = ∵ BAE + 45 °, EAC =