Mathematics problems in Volume 2 of junior high school In RT △ ABC, ∠ C = 90 ° denotes AB = C, BC = a, AC = B (1) If a: C = 1 / 2, B: C (2) If a: C = √ 2 √ 3, C = 6 √ 3, find B If, can write mathematics problem. There are also those with voice. +Q371099102 help me write some other math problems. Thank you. Thank you very much.

Say the inverse proposition of the proposition "if a, B and C are the three sides of △ ABC, and satisfy a & sup2; C & sup2; - B & sup2; C & sup2; = a ^ 4-b ^ 4, then △ ABC is a right triangle", judge the truth of the original proposition and the inverse proposition, and give the proof

When the value of a is, the solution of the equation {3x + 2A = 1 2x-3y = 1-A satisfies x > 0 and Y is less than or equal to 0?
Why I've done it 800 times and still have no solution --

If a is known, find XY
X=(1-2A)/3
(1-2A)/3>0 A

The starting price of a taxi in a city is 7 yuan when the distance is less than 3 km. When the distance is more than 3 km, the taxi will be charged 1.4 yuan per kilometer (less than 1 km is calculated as one kilometer)?

Pay 21 > 7
So the journey is more than 3km
Let his journey be XKM
Then 7 + (x-3) * 1.4 = 21
The solution is x = 13
Therefore, the range of travel is 13-14km, because less than 1km is calculated as 1km

A company has invested in the construction of a shopping mall with 30 shops. It is predicted that when the annual rent of each shop is set at 100000 yuan, all the shops can be rented out. For every 5000 yuan increase in the annual rent of each shop, one less shop will be rented out. The company will pay 10000 yuan for each shop rented out and 5000 yuan for each shop not rented out
(1) When the annual rent of each shop is set at 10000 yuan, the company's annual income (income = rent - various expenses) is 2.75 million yuan?
(2) Can the annual income of the company reach 2.9 million yuan? If so, please give us the annual rent of each shop
Answer (1) 150000 yuan or 105000 yuan
(2) No

1. Suppose that the annual rent of each shop is x ten thousand yuan, the company's annual income is 2.75 million yuan
When x = 100000, the income is 2.7 million, so x can only be greater than 100000
Then, the number of rooms not rented is: (X-10) / 0.5 = t, and the number of rooms rented is: 30-t
Rent: (30-t) * x fees paid by non leased shops: 0.5T fees paid by leased shops: (30-t) * 1
Therefore, the total income is: Rent - fees paid by unlicensed shops - fees paid by leased shops = [(30-t) * x] - [0.5T - (30-t) * 1]
Simplify the quadratic equation of one variable: (- 2 times the square of x) + 51x-40 = 275 △ = 51x51-4x (- 2) x315 = 81
According to the root formula, X1 = 15, X2 = 10.5
2. From one, we can see that the equation of income is: (- 2 times the square of x) + 51x-40 = 290 test △ = 51x51-4x (- 2) x330 = - 39, which is less than 0, so the equation has no root, so the income cannot reach 2.9 million yuan

1. X & sup2; - 3x times (X & sup2; - 9)

Original formula = x & sup2; - 3x of X & sup3; - 9x
=X (x-3) of X (X & sup2; - 9)
=X (x + 3) (x-3)
=x+3

The translation efficiency of an electronic receiver is 75 times that of manual translation. It takes 2 hours and 28 minutes less to translate 3 000 words than manual translation
A. 78 000，1 200B. 12 000，78 000C. 97 500，13 000D. 90 000，1 200

Suppose that the number of words per minute translated by human is x, then the number of words per minute translated by the electronic receiver is 75X. According to the meaning of the title, 3000x-300075x = 2 × 60 + 28, and the solution is x = 20. After testing, x = 20 is the root of the original equation, 75X = 1500

Car a and car B carry a batch of goods together. Car a carries 8 / 13 of all the goods. How much more does car a carry than car B?

Car a carries 8 / 13 of all the goods, while car B carries 5 / 13 of all the goods. Car a carries 3 / 13 more than car B
Car B: 1-8 / 13 = 5 / 13
A is more than B: 8 / 13-5 / 13 = 3 / 13
If you want to make a decimal, 3 / 13 = 0.230769

Ning Ning went to his uncle's house as a guest. His aunt took out a large plate of fruit and said to him, "these are all your favorite fruits, but I'll test you first. There are 12 apples, grapefruit and pineapple on the plate. The number of grapefruit is twice that of pineapple. If you take out four, there will always be at least one apple. Do you know how many of these three fruits are there?

Apple a, grapefruit B, pineapple C. A + B + C = 12b = 2ca + 3C = 12a = 12-3c, apple 9, grapefruit 2, pineapple 1, the difficulty of this problem is "take out four at least one apple". This sentence is equivalent to what? That is to say, maybe all four are apples, maybe three in four, maybe two, but how all

A barrel of salad oil weighs 200 kg. After half of the oil is sold, the barrel weighs 110 kg. How many kg of oil is there in the barrel

(200-110)×2=180kg