If the length of a cuboid is increased by 5 cm, its surface area will be increased by 80 square cm

If the length of a cuboid is increased by 5 cm, its surface area will be increased by 80 square cm

Section perimeter: 80 / 5 = 16 cm
Side length of section: 16 / 4 = 4cm
Cuboid surface area: 4 * 4 * 2 + 40 * 4 * 4 = 672 square centimeters

If the length of a cuboid is increased by 5 cm, its surface area will be increased by 80 square cm
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It can't be four

The side length of the original section is 80 / (4 * 5) = 4cm
Surface area: 2 * 2 * 4 * 4 + 2 * 40 * 4 = 64 + 320 = 384 square centimeter

Given a = x2-2x + 1, B = 2x2-6x + 3. Find: (1) a + 2B. (2) 2a-b

(1) According to the meaning of the title: a + 2B = x2-2x + 1 + 2 (2x2-6x + 3), = x2-2x + 1 + 4x2-12x + 6, = 5x2-14x + 7. (2) 2a-b = 2 (x2-2x + 1) - (2x2-6x + 3), = 2x2-4x + 2-2x2 + 6x-3, = 2x-1

I love your sign language. What's the origin of this gesture?

Add a monomial to the polynomial 16x & sup2; + 1 to make it a complete square. Please write all the monomials that meet the conditions
Come on! Good bonus points

16x²=(4x)² 1=1²
It can be added with 8x or - 8x;
If 16x & # is equal to the first term, then the term equivalent to the second term is 64x ^ 4
So it can be 8x or - 8x or 64x ^ 4

19: 30-21:45 is the conversion formula of () minutes () hours
Formula, formula!

... speechless
One hour, 60 minutes,
21 hours 45 minutes - 19 hours 30 minutes = 2 hours 15 minutes = 2 * 60 + 15 = 135 minutes
21 hours 45 minutes - 19 hours 30 minutes = 2 hours 15 minutes = 2 + 15 / 60 = 2 + 0.25 = 2.25 hours

It is known that the integer solutions of the system of linear inequalities with one variable {x + 3 ＞ a, X-1 ＜ B} about X are 0 and 1. The range of values of a and B is obtained
It is known that the integer solutions of the system of linear inequalities of one variable {x + 3 ＞ a, X-1 ＜ B} about X are 0 and 1. The range of values of a and B is obtained
I get x ＞ A-3, X ＜ 1 + B, because the integer solution of X is 0,1, so I get A-3 ＜ x ＜ 1 + B on the number axis. But the teacher said that the last column - 1 ≤ A-3 ＜ 0,1 ＜ B + 1 ≤ 2 can be equal to ah, I can't think of its solution

Integer solutions are 0 and 1
A-3 < x < 1 + B
therefore
-1≤a-3＜0,1＜b+1≤2
2 ≤ a < 3, 0 < B ≤ 1
Why can be equal to
Because A-3 ＜ x ＜ 1 + B in the solution set is not equal to, finding a and B can be equal to
For example, a = 2, B = 1
In this case, the solution set of X is - 1 < x < 2, and its integer solutions are 0 and 1

There are three classes planting trees in Grade 6 of experimental primary school. The number of trees planted in class 1 accounts for 14% of the total number of trees in the three classes. The ratio of trees planted in class 2 to class 3 is 3:4. The number of trees planted in class 2 is 24 less than that in class 3. How many trees are planted in each of the three classes?

24 ／ 4 − 34 = 96 (trees) 96-24 = 72 (trees) (96 + 72) ／ (1-14) × 14 = 168 × 43 × 14 = 56 (trees) a: 56 trees are planted in class one, 72 trees in class two and 96 trees in class three

Given the function f (x) = - x + 1, x < 0, f (x) = X-1, X ≥ 0, then the solution set ()
A. {x|x≤2−1}B. {x|x≥1+2}C. {x|x＜1+2}D. {x|x＞1+2}

When x + 1 ＜ 0, i.e. x ＜ - 1, the inequality x + (x + 1) f (x + 1) ≤ 1 has the same solution to x + (x + 1) [- (x + 1) + 1] ≤ 1, i.e. x2 ≥ - 1, then x ＜ - 1. When x + 1 ≥ 0, i.e. x ≥ - 1, the inequality x + (x + 1) f (x + 1) ≤ 1 has the same solution to x2 + 2x-1 ≤ 0, and the solution is − 1 − 2 ≤ x ≤ 2 − 1, then − 1 ≤ x ≤ 2 − 1

After a shopping mall bought two kinds of goods, the price of goods a was increased by 50%, and that of goods B was increased by 40% as the price. It was new year's day when the shopping mall held promotional activities, and the price of goods a was increased
A customer pays 538 yuan for one piece of commodity a and B. the total profit of the store is 88 yuan. How much is the purchase price of the two commodities

Let a's price be x and B's price be y
The selling price of a is 1.5x and that of B is 1.4y
Then 1.5x times 0.8 + 1.4y times 0.85 = 538
538-x-y=88
The solution is x = 250, y = 200