What number should be filled in this place and how to get it? 2 26.4 6.6 6 13.6 1.7 10.8 2.7 What number should be filled in the question mark and how to get it?

What number should be filled in this place and how to get it? 2 26.4 6.6 6 13.6 1.7 10.8 2.7 What number should be filled in the question mark and how to get it?

Fill in 2, because (2 + 2) * 6.6 = 26.4
(6+2)*1.7=13.6
+2)*2.7=10.8
=2

Figure number reasoning (what should be filled in the question mark? What is the law between them?)
3 15 23 18
30 9 19
7 31 21
27 11 24 15

According to the graph route, 3 + 30 = 33,7 + 27 = 34,11 + 24 = 35,15 + 21 = 36,19 + 18 = 37,23 + 15 = 38, = 39,9 + 31 = 40. So the sum of the two unknowns is 39. The answers to this question at that time are 27 and 12

In rectangular paper ABCD, ab = 3cm, BC = 4cm, now fold and flatten the paper so that a and C coincide. If the crease is set to EF, then the area of the overlapping part △ AEF is equal to ()
A. 738B. 758C. 7316D. 7516

Let AE = x, from folding, EC = x, be = 4-x, in RT △ Abe, AB2 + be2 = AE2, i.e. 32 + (4-x) 2 = X2, the solution is: x = 258; from folding, we can see that ∠ AEF = ∠ CEF, from ad ‖ BC, we can get ∠ CEF = ∠ AFE, i.e. AE = AF = 258; ｜ s △ AEF = 12 × AF × AB = 12 × 258 × 3 = 7516

It is known that the equation (K & sup2; - 4) x & sup2; + (K + 2) x + (K-6) y = K + 8 is an equation about X, Y. when k is a value, the equation is one variable and one power

According to the meaning of the title:
K & sup2; - 4 = 0 or K + 2 = 0
therefore
When k = - 2
The equation is one variable one power

There are two points a (- 1,0), B (1,0) on the plane, and point P is on the circumference (x-3) 2 + (y-4) 2 = 4. Find the coordinates of point P when ap2 + bp2 is the minimum

According to the meaning of the title, if we make the symmetric point Q of point P about the origin, then the quadrilateral paqb is a parallelogram. According to the properties of parallelogram, there are ap2 + bp2 = 12 (4op2 + AB2), that is, when OP is the minimum, ap2 + bp2 takes the minimum, opmin = 5-2 = 3, PX = 3 × 35 = 95, py = 3 × 45 = 125, P (95125)

Factoring in real numbers: 3x ^ 2-x-1=____________

=3(x²-x/3-1/3)
=3(x²-x/3+1/36-1/36+1/3)
=3[(x-1/6)²-(√13/6)²]
=3(x-1/6+√13/6)(x-1/6-√13/6)

In the cube abcd-a1b1c1d1 with edge length a, point E is the midpoint of AD, and the angle between BD1 and plane ad1e is calculated

The angle between BD1 and plane ad1e is ∠ bd1a, AD1 is (root 2) a, BD1 is (root 3) a, AB is a, so in RT △ abd1, the sine value of ∠ bd1a is three thirds of the root

How to prove that the n-th power of sequence an = (1 + 1 / N) is monotone increasing sequence

The following information is provided for reference
There are a lot of methods
1.an=(1+1/n)^n=
=1+C（n,1）1/n+C（n,2）（1/n）^2+..+（1/n）^n=
=1+1+（1-1/n）（1/2!）+（1-1/n）（1-2/n）（1/3!）+..+
+（1-1/n）（1-2/n）..（1-（n-1）/n）（1/n!）.
2.1-k/n

PA, Pb and PC are three rays starting from point P. the angle between each two rays is 60 degrees. Then the cosine of the angle between PC and PAB is ()
A. 12B. 22C. 33D. 63

Take any point D in PC and make do ⊥ plane APB, then ∠ DPO is the angle between PC and plane PAB; Because do \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\switchto DP O = oppd = 33. That is to say, the cosine of the angle between the line PC and the plane PAB is 33

Simple calculation of 301 × 79
Three hours only

301×79
= 79×(300+1)
= 79×300 + 79
= 300×(80-1) + 79
= 24000 - 300 + 79
= 23779