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X1, 2x... X2011 are all positive numbers, a = (x1 + x2... + x2010) (x2 + X3... + x2011) B = (x1 + x2... + x2011) (x2 + X3... + x2010) Compare the size of a and B
Let m = x2 + X3 + +x2010
a=（X1+M）(M+X2011)=M^2+（X1+X2011）M+X1`X2011
b=(X1+M+X2011)M=X1M+M^2+MX2011
Obviously, a is more than B by X1 * x2011
So a > b
Do you understand?
There are 30 boys in class 61, and girls account for 5 / 6 of the boys. How many students are there in this class
30 △ 5 / 6 + 30 = 55 persons
If A-B = B-C = 3 / 5, a & sup2; + B & sup2; + C & sup2;, then AB + BC + ca=
There are 50 boys and the ratio of boys to girls is 5 to 3. How many girls are there?
This is a basic problem in Grade 6. 50 divided by 5 = 10 The quantity of a portion
And then 10 times 3 = 30 girl student
If X-Y = 5, xy = 6, then what is XY XY
Xy-xy = XY (X-Y) = X-Y = 5, xy = 6, ■ = 6 * 5 = 30
There are 36 students in the art group of the experimental primary school, and the number of girls is 80% of that of boys. How many boys and girls are there in the art group?
Boys: 36 △ 1.8, = 20; girls: 36-20 = 16 or 20 × 80% = 16; a: there are 20 boys and 16 girls
What is the root of 1 and 0
1 square root = 1
0 square root = 0
If a, B and C buy a TV set together, half of the amount paid by a is one third of the amount paid by B, and three seventh of the amount paid by C. It is known that C pays 120 more than a
It is known that C pays 120 yuan more than a, how much is this TV set
Let a pay X Yuan, B pay y yuan and C pay Z yuan
1/2x=1/3y,y=3/2x
1/2x=3/7z,z=7/6x
x:y:z=6:9:7
z-x=120
7a-6a=120;a=120
6A + 7a + 9A = 22a = 2640 yuan
If the result of division of two numbers is negative, how many negative factors are there? If the result of division of three numbers is negative, how many negative factors are there?
How about the division of four numbers, five numbers and six numbers? First observe and find out the law, and then answer: if the division result of 2011 numbers is negative, how many possibilities are there for the number of negative factors?
If the division of two numbers is negative, there is one negative factor
If the result of division of three numbers is negative, there are 1 or 3 negative factors,
Four numbers with one or three negative factors,
Five numbers, one or three or five negative factors
Six numbers with one or three or five negative factors
If the division result of 2011 numbers is negative, then the number of negative factors has (2011 + 1) △ 2 = 1006 possibilities
A, B and C went to buy books. The number of books B bought was 37 more than that of a, and the number of books c bought was 25 less than that of A. then, the three bought at least one book______ This is a book
Let a buy x books, the total number of books bought by three people: x + 37x + 3 + 25x-1, = 6435x + 2, when a buys the least books, that is, x = 35, three people buy the least books, 35 + 35 × 37 + 3 + 35 × 25-1, = 35 + 15 + 3 + 14-1, = 66 (Books). A: the total number of books bought by three people is at least 66, so they should fill in: 66
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