Let the sum of the first n terms of the arithmetic sequence {an} be Sn, A2 + A4 = 6, then S5=______ ．

Let the sum of the first n terms of the arithmetic sequence {an} be Sn, A2 + A4 = 6, then S5=______ ．

According to the properties of arithmetic sequence, a1 + A5 = A2 + A4 = 6, and S5 = 5 (a1 + A5) 2 = 5 × 62 = 15, so the answer is: 15

M is a constant. When x 2 + m x 1 / 25 is a complete square, what is the value of M?

Can you store it
X 1 / 25 is one

In △ ABC, ab = AC, D is the upper point of BC, e is the upper point of AC, ad = AE, ∠ BDC = 30 °, find ∠ EDC
Draw your own picture
∠BAD=30°

That's right
∠C＝1/2(180°－∠BAC)
∠AED＝1/2(180°－∠DAE)
∴∠EDC
＝∠AED－∠C
＝1/2(180°－∠DAE)－1/2(180°－∠BAC)
＝1/2(180°－∠DAE－180°＋∠BAC)
＝1/2(∠BAC－∠DAE)
＝1/2∠BAD
＝15°

(x-1) (x + 1) (2nd power of X + 1) - (4th power of X + 1)

(x-1) (x + 1) (2nd power of X + 1) - (4th power of X + 1)
=（X^2-1）(x^2+1)-（x^4+1）
=(x^4-1)-（x^4+1）
=-2

Among the points representing integers (except the origin) on the number axis, the point closest to the origin has______ The number is______ ．

As shown in the figure: it can be seen from the figure that there are two points closest to the origin, namely ± 1. So the answer is: 2, ± 1

1. Given that y = f (x) is an odd function defined on R and an increasing function on R, the solution set of the inequality f (x ^ 2-4x-5) > 0 is obtained
2. Let f (x) be an odd function defined on [- 1,1], and for any a, B ∈ [- 1,1], if a + B ≠ 0, f (a) + F (b) / A + b > 0
(1) If a > b, compare f (a) with F (b)
(2) Solve the inequality f (x-1 / 2) 0) and have four different roots x1, X2, X3 and X4 on the interval [- 8,8]. Then what is X1 + x2 + X3 + X4?

1.
∵ y = f (x) is an odd function and an increasing function
∴x^2-4x-5>0
x^2-4x-5=(x-5)(x+1)>0
Ψ x > 5 or X

Why is the voltage between any line and zero line of three-phase 380V 220 V
I don't understand the principle of three-phase electricity

The waveform of alternating current is a bit like the shape of a pile of earth. When a fire is zero, a pile of earth produces a voltage of 220 V, while when three phases are equal to two thirds of the diameter of the pile of earth, another pile of earth is piled up. The height of the two piles is 1.732 times of the highest height of a pile of earth

Who has the second grade math problem! Urgent!
OK + 10 points

Fraction exercises 1. And______ Same, called______ Scores+=______ The rule is________________ With______ Same, called_______ Fraction, ±=_______ The rule is:____________ 2. With______ Different, called______ Scores+=______ The operation method is____ ...

When the resistance increases to 8000, how many degrees will the meter be in 5 hours with a 2000W induction cooker?

2kW * 5h = 10kW. H = 10 degrees

1. How to distinguish the general score from the approximate score? 2. How to know whether to use the general score or the approximate score in an applied problem?

General score is to change two different fractions into the same and the denominator is equal
The reduction of a fraction into a fraction equal to it but with smaller numerator and denominator