If we know that x is an integer and 2x + 3 + 23 − x + 2x + 18x2 − 9 is an integer, then x is () A. 2 b. 3 C. 4 d. 5

If we know that x is an integer and 2x + 3 + 23 − x + 2x + 18x2 − 9 is an integer, then x is () A. 2 b. 3 C. 4 d. 5

The original formula = 2 (x − 3) − 2 (x + 3) + 2x + 18 (x + 3) (x − 3) = 2 (x + 3) (x + 3) (x − 3) = 2x − 3, when x-3 = 2, i.e. x = 5, the original formula value is an integer; when x-3 = 1, i.e. x = 4, the original formula value is an integer; when x-3 = - 1, i.e. x = 2, the original formula value is an integer; when x-3 = - 2, i.e. x = 1, the original formula value is an integer, the symbol

Given that x is an integer, and X + 2 / 3 + "2 / 3-x" + "2x / 9 of X + 18" is an integer, find all the values of X that meet the conditions

Original formula = (2x-6-2x-6 + 2x + 18) / (X & # 178; - 9)
=(2x+6)/(x-3)(x+3)
=2/(x-3);
X-3 = ± 1 or ± 2;
X = 4,2,5 or 1;
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Given that x is an integer, and X + 2 / 3 plus 3-2 / x plus the square of x minus 2 / 9 plus 18 is an integer, we can find the sum of all the values of X that meet the conditions

Original formula = 2 / (x + 3) - 2 / (x-3) + (2x + 18) / (x + 3) (x-3)
=(2x-6-2x-6+2x+18)/(x+3)(x-3)
=2(x+3)/(x+3)(x-3)
=2 / (x-3) is an integer
So x-3 is a divisor of 2
x-3=±1,±2
x=2,x=4,x=1,x=5
So sum = 2 + 4 + 1 + 5 = 12

There are five numbers, the average of which is 92. The average of the first three numbers is 93, and the average of the last three numbers is 89. Do you know what the middle number is?

(93 × 3 + 89 × 3) - 92 × 5, = (279 + 267) - 460, = 546-460, = 86

There are five numbers, the average of which is 92. The average of the first three numbers is 93, and the average of the last three numbers is 89. Do you know what the middle number is?

(93 × 3 + 89 × 3) - 92 × 5, = (279 + 267) - 460, = 546-460, = 86

There are five numbers, the average of which is 92. The average of the first three numbers is 93, and the average of the last three numbers is 89. Do you know what the middle number is?

(93 × 3 + 89 × 3) - 92 × 5, = (279 + 267) - 460, = 546-460, = 86

To process a batch of machine parts within the specified time, if Party A does it alone, it will be completed within the specified time. If Party B does it alone, it will take more than three days to complete it. Now Party A and Party B work together for two days, and then Party B will do it alone, just on schedule, and calculate the original specified number of days

Suppose the original number of days is x, then a does 1 / X every day,
If Party B does it alone, it will take more than 3 days, then Party B does 1 / (x + 3) per day
Then 2 * (1 / x + 1 / (x + 3)) + 1 / (x + 3) * (X-2) = 1
The solution is x = 6

For a batch of machine parts, Party A can complete 5 / 8 of the total number of parts in 5 days, while Party B takes 2 days less than Party A to make this batch of parts alone
When B finished equation a, how many parts were less than 1 / 160

The number of days required for Party A to complete the task alone is 5 ^ (5 / 8) = 8 days, and the number of days required for Party B to complete the task alone is 8-2 = 6 days. After three days of cooperation, the remaining tasks are 1 - (1 / 8 + 1 / 6) X3 = 1 / 8, and Party B has made 1 / 10 of the total number of parts, which proves that Party A has made 1 / 8-1 / 10 of the total number of parts = 1 / 40, and the total number of parts is 160 ^ (1 / 40

There are five numbers, the average of which is 92. The average of the first three numbers is 93, and the average of the last three numbers is 89. Do you know what the middle number is?

(93 × 3 + 89 × 3) - 92 × 5, = (279 + 267) - 460, = 546-460, = 86

There are five numbers, the average of which is 92. The average of the first three numbers is 93, and the average of the last three numbers is 89. Do you know what the middle number is?

(93 × 3 + 89 × 3) - 92 × 5, = (279 + 267) - 460, = 546-460, = 86