Given X & # 178; + Y & # 178; = 13. X + y = 4, then xy =?

Given X & # 178; + Y & # 178; = 13. X + y = 4, then xy =?

It is known that X & # 178; + Y & # 178; = 13. X + y = 4
Then xy = [(x + y) ² - (X & #178; + Y & #178;)] / 2 = (16-13) / 2 = 3 / 2
If you don't understand, please ask, I wish you a happy study!

Forest plays a very important role in water conservation, soil and water conservation, and flood and drought prevention. According to experts' estimation, there are 100000 mu of land
1. Forest is called "water swallowing and rain spitting machine" by scientists because forest is called "carbon swallowing and oxygen spitting machine", That's because of the forest. 3. What kind of disaster will forest damage cause?

1. Forest has the function of water conservation, water and soil conservation and flood and drought prevention
2. The forest absorbs the carbon dioxide in the atmosphere and exhales fresh oxygen to regulate the temperature
3. The main performance is global warming. Global warming has a huge impact on human production and life, and even threatens human survival. Because of global warming, water evaporation is accelerated, which changes the air circulation and aggravates climate change, thus causing heat waves, hurricanes, rainstorms, floods and droughts

When a = 1 and B = 2, the value of the square of the algebraic formula 3ab-2a, the square of b-4ab + the square of 5A is______

The algebraic formula can be changed into 3A ^ 2b-ab ^ 2 = AB (3a-b). Substituting a = 1 and B = 2 into the above formula, we get 2

In order to thank customers, mineral water manufacturers have launched a "buy four and get one free" campaign. Originally, each bottle of mineral water costs 1 yuan, but now what's the actual discount?
OK, add 20

The price of each bottle of water after buying four for free: (1 * 4) / (4 + 1) = 0.8
Each bottle of water is cheap: 1-0.8 = 0.2
2 / 1 = 20%

Answers to listening questions on page 73 of new concept English 1B?

Dinner's ready Hurry upyou must go wash firsthere is in my roomThere's lots of with us welcomemust call his mother go and wash both Where are you on the tableHere I am I'm late harm doneSalmon and new...

Passenger cars and freight cars depart from a and B at the same time. Passenger cars travel 60 kilometers per hour, and freight cars travel 1 / 15 of the whole journey per hour
The topic is not finished: the bus and the truck leave from a and B at the same time. The bus runs 60 kilometers per hour, and the truck runs 1 / 15 of the whole journey per hour. When they meet, the distance between the bus and the truck is not 5:4. How many meters is the distance between a and B?

When we meet, the distance between the bus and the truck is 5:4
If yes, then:
They met at [4 / (5 + 4)] / (1 / 15) = 20 / 3
So the distance of the bus is: 60 * 20 / 3 = 400
therefore
Distance between Party A and Party B:
400 * (5 / (4 + 5)) = 720 (km)

Given that x = 2 is the solution of the equation (3-ax) / 2 = x / 3 + 2A (a is a known number), find the value of A

x=2
So (3-2a) / 2 = 2 / 3 + 2A
Double two on both sides
3-2a=4/3+4a
6a=5/3
a=5/18

The speed ratio of car a and car B is
A, B two cars from 150 kilometers away from a, B two places at the same time, two minutes of three hours meet, a, B two cars speed ratio is 2:3, a, B two cars every hour how many kilometers? To formula, not equation!

It is known that s = 150km, t = 1.5h, then if the speed of car a is x, and the speed of car B is y, then there are:
Equation 1: 2x = 3Y,
Equation 2: (x + y) × 3 / 2 = 150,
The speed of car a is 40km / h, and that of car B is 60km / h
The formula is as follows: the whole journey is 150 km, the time is 1.5 hours, the speed ratio of the two cars is 2:3, so. S = ut
It is calculated that the speed sum of the two vehicles is 100km in 1.5 hours, and because the speed ratio of vehicle a and vehicle B is 2:3, the speed of vehicle a is (2 / 5) × 100 = 40km,
The speed of car B is (3 / 5) × 100 = 60km

Find a solution to the equation: 2x-37.5% x = 7 / 16

2/3x-37.5%x=7/16
2/3x-3/8x=7/16
7/24x=7/16
x=7/16*24/7
x=3/2

Party A and Party B move forward evenly in the same direction on the highway. The speed of Party A is 3 kilometers per hour, and that of Party B is 5 kilometers per hour. Party A passes through place a at noon, and Party B passes through place a at 2 p.m. when can party B catch up with place a? How far is it from place a? Use the one yuan linear equation to solve it!

Set t hours after noon to catch up with a
Then 5 (T-2) = 3T and the solution is t = 5
That is to catch up with a at 5 p.m
Distance to the ground A3 * 5 = 15km