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What is the least common multiple of 16 and 72? Fast
"Zhang Keyi is very happy to answer for you!
[answer] 144
Because 16 = 2 × 2 × 2, 72 = 2 × 2 × 3 × 3,
They have a common factor of 2 × 2 × 2, so their least common multiple is
2×2×2×2×3×3＝144
1 / 4, 1 / 6 and 1 / 8
Can't make up proportion
The following propositions are proved to be false by giving counter examples
The center line on one side of a right triangle is equal to half of that side
2. Judge whether the proposition "two parallel lines are cut by the third straight line, and the bisector of the same side inner angle is perpendicular to each other" is true or false, and give the proof
Counterexample: in the right triangle ABC, ∠ a = 90 °, ab = 4, AC = 3, AC = 5, the midpoint of AB is D, and the length of the middle line ad of the right side AB is obtained as root 13 by Pythagorean theorem, which is not equal to half of AB, so it does not hold. (the original problem holds only when the line is a hypotenuse.)
Supplementary question: really
Insert two numbers between 2 and 9, so that the first three numbers are equal difference series, and the last three numbers are equal ratio series. Calculate the two numbers
Let two numbers be a and B respectively
Then 2 + B = 2A, 9A = B & sup2;
Because a and B are between 2 and 9, 2 < a < B < 9
So 9 (2 + b) / 2 = B & sup2;
9+9b/2=b²
(b-9/4)²=9+81/16
B = 15 / 4, a = 23 / 8
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Given that the function FX equals ax + 4 / X to the power of X + 1 is even, then the value of function a is zero
Because f (x) is an even function, so f (- 1) = f (1), you can find a by substituting it!
Unfortunately, one of the eight retired teachers broke down 15 kilometers away from the airport and was unable to drive. At this time, there were only 42 minutes left before the plane stopped checking in. At this time, the only available means of transportation was a car, together with the driver The average speed of the car is 60 km / h. The car has to send the eight people in two batches. If the second batch of people are waiting in place, can all the eight people arrive at the airport in time? Please explain the reason. (2) (solution to the equation) if the car takes the first group of people off and the second group of people walk first, the car takes the first group of people to the airport and immediately returns to pick up the second group of people on foot. If the walking speed of these people is 5km / h, Q: can these eight people get to the airport in time? Please give reasons
(1) Suppose the time taken by car to send the two groups of people to the airport is XH, and the solution is: x = 34, 34 × 60 = 45min ＞ 42min, so the eight people can not arrive at the airport in time. (2) suppose the time taken by car to send the first group of people back to meet the second group of people is XH, then the distance taken by the second group of people in this period is 5xkm, and the time taken by car to send the second group of people is (15 − 5x) 60H According to the meaning of the question: 60x + 5x = 2 × 15, the solution: x = 613, then 15 − 5x60 = 1152613 + 1152 = 3552 ≈ 40min ＜ 42min
Arrange all positive integers into a triangular matrix as follows:
The general formula of the nth row of mathematical sequence is: n (n-1) / 2 + 1, so the third number is n (n-1) / 2 + 3
Calculate the first behavior of n-order determinant (a + x) a a
a+x a a …… a
a a+2x a…… a
a a a+3x…… a
……
a a a …… a+nx
(1) Subtract the first line from the second to the nth lines to get a + x a a-x 2x 0…… 0-x 0 3x…… 0…… -x 0 0 …… Nx (2) add 1 / 2 of the second column, 1 / 3 of the third column, and 1 / N of the nth column to the first column to get a + X + A / 2
How to do question 8 on page 149 of mathematics book of people's Education Press
44 × 2 to the 20th power
Here is a set of numbers arranged in the shape of a "tower":
-1
-1/2 1/3
-1/4 1/5 -1/6
-1/7 1/8 -1/9 1/10
.
What is the seventh number in line 2007?
Please explain why 1 + 2 + 3 +... + 2006 = 2007016
Please be as detailed as possible, because I don't just ask for answers. I hope I can understand this problem through your teaching!
There are n numbers in line n, so there are 1 + 2 + 3 +... + 2006 = 20011015 at the end of line 2006, so the seventh number in line 2007 is 2011022, so the answer is 1 / 2011022. Sorry, there was a little miscalculation at the beginning. The sum formula of arithmetic sequence: S = n.a1 + n (n-1) d / 2S is sum, A1 is the first
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