In the cube abcd-a1b1c1d1, e is the midpoint of AB and F is the midpoint of Aa1. 1. Prove that e, C, D1 and F are coplanar 2. CE, DF1, Da three lines are common

In the cube abcd-a1b1c1d1, e is the midpoint of AB and F is the midpoint of Aa1. 1. Prove that e, C, D1 and F are coplanar 2. CE, DF1, Da three lines are common

As shown in the figure, find point EF, connect fecd1, and then connect A1B
Triangle a1ba is isosceles right triangle, EF is the midpoint of both sides, so EF is the median line of triangle a1ba, so EF is parallel to A1B
Prove that A1B is parallel to d1c, so EF is parallel to d1c, two parallel lines determine a plane, so four points are coplanar

Urgent! 7x + x square = 10 find x

X = 2 or x = 5

Given a = {a, a + D, a + 2D}, B = {a, AQ, a * (the square of Q)}, if a = B, find the value of D, Q

In the first case: a + D = AQ (1), a + 2D = AQ ^ 2 (2) from (1) to a = - D / (1-Q) from (2) to a = - 2D / (1-Q ^ 2) - D / (1-Q) = - 2D / (1-Q ^ 2) to q = 1, d = 0 (rounding off) in the second case: a + D = AQ ^ 2 (1), a + 2D = AQ (2) from

3.4 playing an idiom () 15 points is equal to 1000 yuan playing an idiom () 0 plus 0 playing an idiom ()

3.4 beat one idiom (no three no four)
15 points is equal to 1000 yuan. In ancient times, 15 is called a moment, and 1000 yuan means a thousand yuan
0 plus 0 for one idiom

A parallelogram with a base length of 12cm, a height of 5cm and an oblique length of 8cm, its perimeter

12+8=20
20 * 2 = 40 girth
What's the matter with Guan Gao

It is known that the circumference of the semicircle is 51.4cm. What is the diameter of the semicircle?

Using the formula of semicircle circumference: 51.4 / (3.14 + 2) = 10 cm (radius)
10 * 2 = 20 cm (diameter)
A: the diameter of this semicircle is 20 cm

Tangent equation of curve f (x) = x INX at point x = 1?
To get the derivative of the process!

Its derivative is
LNX + 1 at x = 1, the slope is ln1 + 1
So the tangent equation is y = (ln1 + 1) x - 1

x=15/14+2/7x
How to solve this kind of problem

x=15/14+2/7x
5/7x=15/14
x=(15/14)/(5/7)
=(15 / 14) times (7 / 5)
=3/2

Given that real numbers x and y satisfy the conditions {2x-y + 1 ≥ 0,2x + y ≥ 0, X ≤ 1, the minimum value of Z = x + 3Y is obtained

First, draw the line 2x-y + 1 = 0 and the line 2x + y = 0 and x = 1. First, determine the feasible region, and substitute (0,0) respectively, then enter, and satisfy 2x-y + 1 ≥ 0, X ≤ 1, that is, (0,0) in the feasible region, and then draw x + 3Y = 0. Obviously, at the intersection of x = 1,2x + y = 0, take the minimum value x = 1 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 2x + y = 0 simultaneous & nbsp; y = - 2, so z =

A number is made up of seven tens and four ninths. This number is "and his reciprocal is"

A number is composed of seven tens and four ninths. This number is 70 and four ninths, and his reciprocal is 634 and nine ninths