Master Li wants to weld a rectangular iron box without cover with iron sheet (as shown in the picture). How many square decimeters of iron sheet is needed to make this iron box? How many cubic decimeters is the volume of the iron box?

Can you provide the figures
Length × width + length × height × 2 + width × height × 2 = surface area of iron box (i.e. how much iron sheet is needed)
The length × width × height of the iron box = the volume of the iron box

Use a rectangular sheet of iron 40 cm in length and 30 cm in width to make a 5 cm deep rectangular sheet iron box without cover. Calculate the surface area and volume of the box

30 * 40 = 1200 square centimeter 1200 - (4 * (5 * 5)) = 1100 square centimeter
30-5-5 = 20 cm 40-5-5 = 30 cm 20 * 30 * 5 = 3000 CC
Surface area 1100 square centimeter volume 3000 cubic centimeter

Simple operation of 7 / 9 multiplication (2 / 3 minus 2 / 7)

=7/9×2/3-2/9=6/9×（7/9-1/3）=6/9×24/81=8/27

The function y = ax ^ 2 (a is not equal to 0) intersects the line y = 2x-3 at the speed known by point (1, b)
(1) Finding the value of a and B
(2) When x is what value, y in quadratic function y = ax ^ 2 (a is not equal to 0) increases with the increase of X?
(3) How to find the area of the triangle formed by the intersection and vertex of parabola and straight line y = - 2?

(1) Intersection at point (1, b), that is, the point coordinates satisfy the function analytic formula
b=a(1)^2=2(1)-3
b=a=-1
(2) Because a = - 1, the opening of quadratic function is down, then X

A general score of 11 out of 12, 7 out of 18 and 5 out of 6

33 out of 36, 14 out of 36 and 30 out of 36

How to discuss the left and right limits of exponential function with E as the base?
For example, (1-e ^ x) / X
How to discuss the left and right limit of LIM (1-e ^ - x) / x
x→0

lim(1-e^-x)/x x→0
＝1
lim(1-e^x)/x x→0
＝-1
Take a look at the law of lobita in the book

How much is 1 times 2 times 1 / 3 plus 2 times 3 times 1 / 4 plus 3 times 4 times 1 / 5 plus 11 times 12 times 1 / 13
.......................................

44 out of 12 plus 132 out of 13

The 2nth degree of polynomial a - the N + 1 degree of a - the N-1 degree of 2A what is the common factor of this polynomial

a^2n-a^(n+1)-2a^(n-1)
=a^(n+1)*a^(n-1)-a^2*a^(n-1)-2a^(n-1)
=a^(n-1)[a^(n+1)*-a^2-2]
So the common factor of this polynomial is: A ^ (n-1)

Here is a box of matches and an alcohol lamp. How to design experiments to prove the flame temperature of alcohol lamp

Insert the match stem into the flame horizontally, and take it out about 2 seconds later. You can see that the scorch degree of the match stem is different. The two sides of the match are the blackest, and the black in the middle is the lightest. You can know from the scorch degree (blackening degree) of the match stem in all directions: the temperature of the outer flame is the highest, the temperature of the inner flame is the second, and the temperature of the flame core is the lowest

（m-n)+2n（m-n)
The square of (m-n) + 2n (m-n) factorization

﹙m－n﹚²＋2n﹙m－n﹚＝﹙m－n﹚﹙m－n＋2n﹚＝﹙m－n﹚﹙m＋n﹚.

Master Li wants to weld a rectangular iron box without cover with iron sheet (as shown in the picture). How many square decimeters of iron sheet is needed to make this iron box? How many cubic decimeters is the volume of the iron box?