There is a famous mathematical problem called "installing lights in pagodas". The content is "looking from afar to the seventh floor of the towering pagoda, the red lights will be multiplied; the total number of lights is 381. How many lights are there on the top floor?"

Suppose there are x lights at the bottom of the tower, and the lights on each floor are doubled. The second floor is 2x, the third floor is 4x, and the fourth floor is 4x. The formula is: x + 2 * x + 4 * x + 8 * x + 16 * x + 32 * x + 64 * x = 381127 * x = 381x = 3. The top of the tower is 64 * x, so it is 3 * 64 = 192

When a student calculates "25 + X", he mistook "25 + X" for "25 + X" -- the result is 17, so the correct answer to "25 + X" should be "25 + X"?
If a - (- b) = 0, then the relationship between a and B is?

33 a=-b

How to use the Geometer's Sketchpad to draw a circle with fixed radius and length?
If a point on the Geometer's Sketchpad has been determined to be the center of a circle, just draw another line segment and then draw a circle with this line segment as the length. However, the manual of my Geometer's Sketchpad says that the Geometer's Sketchpad can use length data instead of line segment to represent the length, and the unit explains how to operate. Please teach me,

My version 5.0 Geometer's Sketchpad
1. Click "data" and "new parameter" to open the "new parameter" window. Modify the parameter name by yourself, such as R, and change the value to the value you need. Check the distance below, otherwise it cannot be used as the radius of the circle. Then click OK to close the "new parameter" window
2. Select the center of the circle and the newly created parameter r, click "construct" and select the center and radius of the circle as the circle to make the circle satisfying the condition
Other versions of the estimates are OK, but the new parameter menu is different

As shown in the figure, given the square ABCD with side length a, e is the midpoint of AB, P is the midpoint of CE, and F is the midpoint of BP, calculate the area of BFD of triangle

Area of BFD = a ^ 2 * (1 / 16)
Using Pythagorean theorem, BF = (radical 5 / 8) * a is obtained
The corresponding height of BF is = (radical 5 / 5) * a

Using the image of quadratic function, we can find the approximate roots of the quadratic equation y = x & sup2; - x-4 = 0
Teaching methods

Y = 0 X axis
X2-x-4 = 0 circle with (1 / 2,0) as the center and 4.1 as the radius
The intersection points are (0.5 + 4.1,0) and (0.5-4.1,0)
6 and - 3

In a 5 × 5 square, put a white chess piece first, and then a black chess piece. The two chess pieces are not in the same row or column______ There are two different ways to put it

25 × 16 = 400 (species); a: there are 400 different ways to put them

On which point is the image of function y = (3x-1) / (x + 2) symmetric

The function image is centrosymmetric with respect to (- 2,3) points

First simplify, then evaluate: (A2 + 2Ab + B2 / a2-2ab + B2) 3 times (b2-a2 / A + b) 3, where a = 2, B = - 1

(a2-a2-a2 / A + b) the third power of the (b2-a2 / A / A + b) is the third power of the (b2-a2 / A + b) third power, = [(a + b) [(a + b) [(a + b); (a-b) / (a-b); (a-b); (a-b); (a-b); (a-b); [(a + b) (a-b) (a-b) (a-b) (a-b) (a-b); [[(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + b) [(a + B) (a + b) [(a + b) [(a + b) (a + b) (a-in this paper, the author analyzes the relationship between the two factors

ABCD + CDC = ABC, find a =?, B =?, C =? D =?

Your question doesn't hold. Which four digit plus three digit is three digit?

For a right angle trapezoid, the ratio of the top and bottom is 3:5. If the top is increased by 7 cm and the bottom is increased by 1 cm, it becomes a square. How many square meters is the area of the trapezoid?

Sole: (7 cm - 1 cm) X3 / (5-3) = 9 cm
Bottom: 9cm + (7cm-1cm) = 15cm
Height: 15cm + 1cm = 16cm
The area of trapezoid is (9 cm + 15 cm) x 16 cm / 2 = 192 square cm

There is a famous mathematical problem called "installing lights in pagodas". The content is "looking from afar to the seventh floor of the towering pagoda, the red lights will be multiplied; the total number of lights is 381. How many lights are there on the top floor?"