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The multiplication rule of rational numbers: multiply two numbers, get () with the same sign, get () with different sign, and multiply () together If 0 is multiplied by any number, you will get (). In addition, if 1 is multiplied by any number, you will get () -Multiplying 1 by any number yields ()
The same number is correct
Different signs get negative
Multiplying 0 by any number yields 0
In addition: 1 and any number multiplied by the original number
-Multiplication of 1 by any number yields the opposite of the original number
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To solve the inequality (x + 1) (X-2) > 0, we use the rule of multiplication of two rational numbers. If two numbers are multiplied, the same sign will get positive and the different sign will get negative, so we transform the inequality
System of inequalities: {x + 1 > 0 (1) {X-2 > 0 (2), so the solution set of the system of inequalities is x > 2
No
Multiplication greater than 0
It could be all negative
x+1
Solve the inequality (x + 1) (x-1) < 0, solve the inequality (x + 1) (X-2) > 0, use the rule of multiplication of two rational numbers, multiply two numbers, the same sign is positive,
Question 1: (x + 1) (x-1) < 0
X + 1 ＞ 0 and X-1 ＜ 0 or x + 1 ＜ 0 and X-1 ＞ 0 (obviously not true)
It is found that: - 1 ＜ x ＜ 1 or X ＜ - 1, X ＞ 1 (obviously not true)
Therefore:: - 1 ＜ x ＜ 1
Question 2: (x + 1) (X-2) > 0
X + 1 > 0 and X-2 > 0 or x + 1 < 0 and X-2 < 0
X ＞ 2 or X ＜ - 1
The number of female students in class 6 (1) is two fifths of that of male students. The number of male students is several times more than that of female students. The ratio of female students to that of the whole class is (), and the number of male students accounts for
A fraction of the class
This is the number of people
Three two out of seven is better than seven out of five
One hundred minus one, type one word (I know the answer)
It has to be white
If a, B and C jointly buy a TV set, one third of the amount paid by a is equal to one fourth of the amount paid by B and three quarters of the amount paid by C. A pays more than C
2000 yuan. How much is this TV set?
It's better to use arithmetic. If you can't, you can also use equation
Wrong, wrong, B is actually half!
A: B = 1 / 4:1 / 3 = 3:4 = 9:12
A: C = 3 / 4:1 / 3 = 9:4
A: B: C = 9:12:4
A pays 9-4 more than C = 5
It's 2000 △ 5 = 400 yuan per copy
9 + 12 + 4 = 25
TV set: 400x25 = 10000 yuan
[talent Fenghua team] I'm glad to answer for you!
Judgment: because the square root of 1 / 16 is 1 / 4, 1 / 16 under the root sign is 1 / 4
Judgment questions
Wrong
"1 / 16 under the root sign" = the square root of 1 / 16 = 1 / 4
There are three numbers of a, B and C. The ratio of a to B is 3:4, and the ratio of B to C is 6:7
The ratio of a to B is 3:4, and the ratio of B to C is 6:7,
Na a: B: C = (9): (12): (14)
1 / 2x + 5Y = 3 / 2 binary linear equation
Equations 1
1/2x+5y=3/2
y-0.5x=11.5
linear equation in two unknowns
Equations 2
2（x-y)/3-x+y/4=-1
6(x+y)-4(2x-y)=16
linear equation in two unknowns
With formula
I'm in a hurry
Equations 1
It is simplified to x + 10Y = 3
2y-x=23
Add it up to 12Y = 26, y = 13 / 6, and substitute it into formula 2 to get x = 56 / 3
Equations 2
It is reduced to 4x + 5Y = 12
5y-x=8
By subtracting, we get 5x = 4, x = 4 / 5, and substituting into formula 2, we get y = 44 / 25
How much is one of (6 + 2 √ 5)?
How to calculate the big root set small root? Hurry!
6+2√5
=5+2√5+1
=(√5+1)²
So the original formula = 1 / (√ 5 + 1)
=(√5-1)/(√5+1)(√5-1)
=(√5-1)/(5-1)
=(1/4)√5-1/4
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