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The answer to the evaluation of algebraic formula in the dialing training of the seventh grade mathematics volume I
You have to talk about the topic
If AB = BC = CD = Da, then the value of a − B + C − Da + B − C + D is______ Or______ ．
Let AB = BC = CD = Da = k, then d = AK, C = DK = ak2, B = CK = ak3, a = BK = ak4. Let K4 = 1, that is, k = ± 1. When k = 1, a = b = C = D. the original formula = 0; when k = - 1, then a = - B = C = - D, then the original formula = - 2
Evaluation of algebraic expressions
Xiao Ming is doing a problem: "known a, B, find the difference between a and B, because he is too careless, forget to put brackets in the formula, and calculate a wrong result as: - A ^ 2 + 8b ^ 2-4c ^ 2, now only know a = 2A ^ 2 + 3B ^ 2-3c ^ 2", please help Xiao Ming find out the value of B, and calculate the correct result?
Can you tell me something? I don't understand
B=3a^2+5b^2-c^2
Results - A ^ 2-2b ^ 2-2c ^ 2
If 1 + A / 1-A = 1 + B / 1-B, find the value of (2 + a) (2-A) + B & #
Find (2 + a) (2 + b) + B & # 178;
Because 1 + A / 1-A = 1 + B / 1-B
So a / 1-A = B / 1-b
a-ab=b-ab a=b
（2+a)(2-a)+b²=4-a²+b²=4-（a²-b²）=4
X & # 178; - (x + 2) (X-2) - (x + 3) &# 178;. Ask the masters to answer quickly! Have the correct way to solve the problem!
x²-(x+2)(x-2)-(x+3)²
=x²-（x²-4）-（x²+6x+9)
=x²-x²+4-x²-6x-9
=-x²-6x-5
（a-b)^5=a^5-b^5
And the solution (a + B ^ 3) (a-b) ^ 5 is fast
The first mistake, according to the course of junior one, there is no solution
The second one is to see if you read the question wrong,
The original question should be
（a+b)^3 (a-b)^5
=〔(a+b)(a-b)〕^8
=(a^2-b^2)^8
The distance between a and B is 240 km. The speed of a car is 36 km. The speed of a motorcycle is 2 / 3 of that of a car
Two hours and 30 minutes after the motorcycle started from place B, the car drove from place a to place B. how many hours did the car run into a motorcycle
36 * 2 / 3 = 24 km / h
240 - (24 * 2.5) = 180 km
180 / (36 + 24) = 3 hours
During the Spring Festival, a (a ＞ 0) passengers line up in the waiting room to check in when the station begins to check in. After the check-in, some passengers continue to line up to check in. If passengers increase at a fixed speed, the speed of check-in at the check-in gate is also fixed. If a check-in gate is opened, it will take 30 minutes for all the passengers waiting for check-in to check in If there are two check-in gates, it will take 10 minutes to complete all the passengers waiting for check-in. If you want to complete all the passengers waiting for check-in within 5 minutes, so that the passengers who arrive at the station later can follow the check-in, at least several check-in gates should be opened at the same time? （ ）
A. 2B. 3C. 4D. 5
Set X new passengers per minute after the start of check-in, and check-in speed is y passengers per minute at each check-in gate. Within 5 minutes, all the passengers waiting in line for check-in will be checked out, and N check-in gates need to be opened at the same time. The meaning of the question is: a + 30x = 30y & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; ① a + 10x = 2 × 10Y & nbsp; & nbsp; & nbsp; ② a + 5x ≤ 5 × n × Y & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; ③ From ① and ②, we get: y = 2x, a = 30y-30x = 30x, 30x + 5x ≤ 5 × n × 2x, that is 35x ≤ 10xn, ∵ x > 0, ∵ n ≥ 3.5, and∵ n takes the smallest integer, ∵ n = 4, that is, at least four check-in gates should be opened at the same time
A square table is composed of one table top and four legs. If one cubic meter of wood can be used to make 50 tables or 300 legs of a square table, and there are 5 cubic meters of wood, how many cubic meters of wood can be used to make the table top and how many cubic meters of wood can be used to make the table legs, and the table top and legs can be made into a square table? How many square tables can be made?
According to the meaning of the question, x + y = 550x × 4 = 300y, the solution is x = 3Y = 2, ∵ 1 cubic meter of wood can make 50 table tops of square table, a square table has a table, ∵ 50x = 50 × 3 = 150. ∵ 150 square tables can be made. Answer: 3 cubic meters of table top, 2 cubic meters of table legs, 150 square tables
As shown in the figure, point O is a point on the straight line AB, ∠ cod = 45 °, OE and of divide ∠ AOC and ∠ DOB equally, and calculate the degree of ∠ EOF
∵ - cod = 45 °, ∵ - AOC + ∠ BOD = 180 ° - cod = 180 ° - 45 ° = 135 °, ∵ OE, of are divided into ∵ AOC and ∵ DOB, respectively, ∵ - AOE = ∵ Coe, ∵ DOF = ∵ BOF ∵ EOC + ∠ DOF = 12 (∵ AOC + ∠ BOD) = 67.5 °, ∵ - EOF = ∵ EOC + ∠ DOF + ∠ cod = 67.5 ° + 45 ° = 112.5
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- 1. Algebraic evaluation exercises When A-B / A + B = 3, find the value of algebraic formula 2 (a-b) / (a + b) - 4 (a + b) / 3 (a-b)
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- 3. 1. The absolute value of m plus 2 plus the square of N + 3 equals 0. What is the value of M and N? 2. (m-1) multiply x to the power of m by Y is a binomial about X, y, and find M 3. The absolute value power of M + 1 of polynomial x multiplied by Y square + m multiplied by x square + 1 is a cubic trinomial about X 2、 two m (m-1)x y 3、 |m+1| 2 2 X y +mx +1 And the first question. Can't square be zero?
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- 5. If C is an integer, try to judge the shape of △ ABC
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- 7. Given x = √ 5 + 2, then the square of the algebraic formula x-4x + 3 is
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- 10. Simplification: (- 2A) × a - (- 2A) & # - 178; the result is a.0 b.2a & # - 178; C. - 6A & # - 178; D. - 4A & # - 178
- 11. If the sum of the two numbers is 18 and one of them is represented by the letter X, then the product of the two numbers is expressed algebraically as A.18x B.x(18+x) C.x(x-18) D.x(18-x)
- 12. It is known that monomials only contain the letter X, and their exponents are 3 and 2 respectively. When x = 2 and y = 3, their values are 24, write this algebraic formula
- 13. In the algebraic expression 3x, 3 is called the sum of the letter factor X___ The coefficient of 1 / 2Ab is___ .
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- 15. Given that the value of algebraic formula (x-a) 2 + B is always positive, then the value of B should be () A. Negative number B. non negative number C. non positive number D. positive number
- 16. Please write an algebraic expression containing X. no matter what rational number x takes, the value of the algebraic expression is always non negative
- 17. When Xiao Fang calculates a + bc-a ^ 2 / A ^ 2 + B ^ 2 + C ^ 2 (a, B, C are not equal to each other), he finds that if a and B are exchanged, the value of this formula remains unchanged, If a + B + C = 1, the constant value a + (bc-a ^ 2 / A ^ 2 + B ^ 2 + C ^ 2) bc-a ^ 2 is a molecule
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