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The bus and truck start from two places at the same time, and run in opposite directions. The known speed ratio is 5:7. The meeting place is 30km away from the midpoint of two places. Find the distance between two places
The distance when we met was 5:7
When they met, the bus made a full journey
5 ÷ (5 + 7) = 5 / 12
The distance between the two places
30 (1 / 2-5 / 12) = 360 km
Given log2 (x2-3x-2) + ilog2 (x2 + 2x + 1) > 1, then the value set of real number x is______ ．
∵ log2 (x2-3x-2) + ilog2 (x2 + 2x + 1) > 1, ∵ log2 (x2 + 2x + 1) = 0, ∵ x2 + 2x + 1 = 1, the solution is x = 0, x = - 2. In log2 (x2-3x-2), when x = 0, x2-3x-2 ＜ 0, when x = - 2 is omitted, x2-3x-2 = 8, log28 = 3 ＞ 1, it holds ∵ x = - 2
The speed of a car is 1.5 times that of a motorcycle. The car and motorcycle can travel 300 kilometers in three hours
A: the speed of a car is 60 km / h, and that of a motorcycle is 40 km / h
The univariate quadratic equation refers to an equation with an unknown number and the highest degree of the unknown number is 2. The method to find the solution of the univariate quadratic equation x2-4x-5 = 0 is as follows: the first step is to formulate the term on the left side of the equation about X, (X-2) 2-4-5 = 0, the second step is to keep the square formula on the left side of the equation, and move the rest to the right side of the equation, (X-2) 2 = 9; the third step is to calculate the solution according to the formula of the square The fourth step is to find X. by analogy with the above method of finding the root of quadratic equation with one variable, (1) solving quadratic equation with one variable: 9x2 + 6x-8 = 0; (2) finding the minimum value of algebraic formula 9x2 + Y2 + 6x-4y + 7
(1) 9x2 + 6x-8 = 0, deformation: x2 + 23x = 89, formula: x2 + 23x + 19 = 1, namely (x + 13) 2 = 1, square root: x + 13 = ± 1, solution: X1 = 23, X2 = - 43; (2) 9x2 + Y2 + 6x-4y + 7 = 9 (x2 + 23x + 19) + (y2-4y + 4) + 2 = 9 (x + 13) 2 + (Y-2) 2 + 2, when x = - 13, y = 2, the original formula takes the minimum value of 2
Rearrange the words in a certain order. 1. Universe solar system Milky Way moon earth
Universe, galaxy, solar system, earth and moon (from large to small)
X minus 15 percent is 68. Solve the equation
x-15%x=68
0.85x=68
x=80
Can the friction be increased by increasing the pressure
Isn't it said that the friction force is related to the roughness of the contact surface and the pressure? Then why did someone explain to me the principle of spikes that spikes increase the pressure of the foot on the runway, so as to increase the friction force and prevent the athletes from sliding?
The principle of spikes should be to increase the pressure, that is to make the effect of force more obvious, so that the ground produces greater pressure on the feet, so that athletes can run more easily, right?
Specific problems are analyzed in detail
If in a rigid plane, simply increasing the pressure will not increase the friction
But on the track, the ground is usually a soft rubber surface. As the pressure increases, the nail can grasp the ground, which naturally increases U. from F = UN, it can be concluded that the friction becomes greater. And Newton's second law, f = ma, increases the acceleration. So athletes can run faster
After class, the teacher gave a question on the blackboard, (x + 2 / 2) ≥ (2x-1 / 3) + a number, only knowing that the solution set is x ≤ 2, what is the number
Let this number be a
（x+2/2）≥（2x-1/3）+ a
Multiply both sides by six at the same time, and you get
3(x+2) ≥ 2(2x-1) + 6a
3x+6 ≥ 4x-2+6a
x ≤ 8-6a
Also known
The solution set is x ≤ 2
so
8-6a=2
6a=6
a=1
This number is one
The two trains run from two places 1000 meters apart at the same time. The two trains don't meet each other in 6 hours. The distance is 135 kilometers. The first train runs 85 kilometers per hour. How many kilometers per hour does the second train run? The solution of the equation
If vehicle B travels x kilometers per hour, there will be
（85+X）*6=1000-135
（85+X）*6=865
85+X=865/6
X=865/6-85
X=355/6
A and B are two natural numbers which satisfy the following two conditions at the same time
A and B are two natural numbers which satisfy the following two conditions at the same time
(1) (2) a + B = 17
Find the value of a and B
1/5
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