If the values of 5x + 9 and - 3x + 3 are opposite to each other, then the value of X is

If the values of 5x + 9 and - 3x + 3 are opposite to each other, then the value of X is

5x+9=3x-3
2x=-12
x=-6

The original price of a drug is 100 yuan. After two successive price reductions, the price becomes 64 yuan. If the percentage of each price reduction is the same, then the percentage of each price reduction is ()
A. 40%B. 30%C. 20%D. 10%

Let the average percentage of each price reduction be X. according to the equation, we get 100 × (1-x) 2 = 64, and the solution is X1 = 0.2 = 20%, X2 = 1.8

The number is 9 less than 3 times of X, which can be expressed as 3x + 9. Why is it wrong

What 3x + 9 stands for is that a number is nine times more than three times X
A number is 9 less than three times x, which can be expressed as 3x-9

The original price of a commodity is 100 yuan. After two successive price cuts, the selling price is 81 yuan. What is the average percentage of each price cut?

The average price reduction of the product is X
100×﹙1－x﹚²＝81
X = 0.1 = 10%, x = - 1.1 (rounding off)
The average price reduction of the product is 10%

The number of real roots of the equation lg2x - [lgx] - 2 = 0 is
Is there any other method that does not start with drawing? Is there any strict mathematical language proof?

Because lg2x = [lgx] + 2
The right side is an integer, so the left side also needs to be an integer, set to K
Then lg2x = k = [lgx] + 2
2x=10^k
x=1/2*10^k
So k = [lgx] + 2 = [k-lg2] + 2 = K + 2 + [- LG2] = K + 2-1 = K + 1
So the equation has no real roots

The original price of a product is 800 yuan per piece. After two price cuts, the percentage of each price cut is the same. Now the price of each piece is 578 yuan, and the percentage of each price cut is calculated

Suppose the percentage of each price reduction is X: the price after the first price reduction: 800-800x = 800 (1-x); the price after the second price reduction: 800 (1-x) - 800 (1-x) x; 800 (1-x) - 800 (1-x) x = 578800 (1-x) (1-x) = 578 (1-x) & # 178; = 578 / 8001-x = ± 17 / 20x1 = 1-17 / 20 = (100-85) / 100 = 15%; x2 = 1 + 1

For a real number x, the sign [x] denotes the largest integer not exceeding x, for example, [π] = 3, [- 1.08] = - 2, define the function f (x) = x - [x], then the correct one in the following proposition is ()
A. The maximum value of function f (x) is 1b. The equation f (x) = 12 has only one solution. C. function f (x) is a periodic function D. function f (x) is an increasing function

From the meaning of the question, we can know that: F (x) = x - [x] ∈ [0,1], the maximum value of the function f (x) is 1, a is wrong; we also know that the function repeats once every other unit, so the function is a function with a period of 1. So C is correct, B is incorrect, and D is incorrect

The original price of 600 yuan is 384 Yuan due to two price cuts. If the percentage of the two price cuts is the same, what is the price after the first price cut?
Can set the unknown, speed answer! Immediately adopt!

Set the price reduction x (commonly known as discount),
600*X*X=384
X = 0.8
That's 20% off,
After the first price reduction, it is 600 * 0.8 = 480

【x】 Represents the largest integer not exceeding the real number x, then [log2 1] + [log2 2] + [log2 3] +. + [log2 2012] is equal to?

【log2 1】=0,【log2 2】=1,【log2 3】=1,【log2 4】=2,【log2 5】=2,【log2 6】=2,
【log2 7】=2,【log2 8】=3……
2^1=2, 2^2=4, 2^3=8, 2^4=16, 2^5=32, 2^6=64, 2^7=128, 2^8=256, 2^9=512,
2^10=1024,2^11=2040>2012.
According to the above rule, the first number is 0, the second to third numbers are 1, and the fourth to seventh numbers are 2
Because 2 ^ 11 = 2040 > 2012, the number from 512 to 2012 is 10
【log2 1]+[log2 2]+[log2 3]+.+[log2 2012]=2*1+(7-3)*2+(15-7)*3+(31-15)*4+(63-31)*5
+(127-63)*6+(255-127)*7+(511-255)*8+
(1023-511）*9+(2012-1023)*10=2*1+4*2+8*3+16*4+32*5+64*6+128*7+256*8+512*9
+989*10=18084.

The price of a commodity has been reduced twice in a row. The total price has been reduced by 19%. The average percentage of each reduction is

If the price reduction rate is r, then
(1-r)^2=1-19%
r=10%