① 1 / 5 + 1 / 3 = 8 / 15, ② 8 / 15 × 1 / 2 = 4 / 15, ③ 3 / 5-4 / 15 = 1 / 3 Synthesis formula and operation order

① 1 / 5 + 1 / 3 = 8 / 15, ② 8 / 15 × 1 / 2 = 4 / 15, ③ 3 / 5-4 / 15 = 1 / 3 Synthesis formula and operation order

Comprehensive formula:
3 / 5 - (1 / 5 + 1 / 3) × 1 / 2
Operation order:
1. Addition: 1 / 5 + 1 / 3
2. Multiplication: 8 / 15 × 1 / 2
3. Subtraction: 3 / 5-4 / 15

4 out of 5 of a number is 8 more than 2 out of 3 of this number

8÷(4/5-2/3)
=8÷(12/15-10/15)
=8÷2/15
=8x15/2
=60

On the problem of space rectangular coordinate system
The distance from any point P (x, y, z) in the space rectangular coordinate system oxyz to the origin o is / op / = root sign (x square + y square + Z Square). If / op / fixed length R, then x square + y square + Z square = R square. What figure does it represent? (p.137, compulsory mathematics 2)

X square + y square + Z square = R square, which means that the distance from each point of the figure to the center of the circle is r, and the figure is a ball

If the right branch of the straight line L: y = KX + 1 and hyperbola C: 2x2-y2 = 1 intersect at two different points a and B, then the value range of the real number k is ()
A. − 2 ＜ K ＜ 2B. - 2 ＜ K ＜ 2C. K2 ＜ 4 and K2 ≠ 2D. - 2 ＜ K ＜ 0 and K ≠ − 2

After substituting the equation y = KX + 1 of the straight line l into the equation 2x2-y2 = 1 of the hyperbola C, we get (k2-2) x2 + 2kx + 2 = 0. According to the meaning of the problem, the right branch of the hyperbola C and the straight line L intersect at two different points. Let the coordinates of the two intersections be (x1, Y1), (X2, Y2), (x1, Y1), (X2, Y2) at the right branch of the hyperbola C,  x1 ＞ 0, X2 ＞ 0, ｜ X1 + x2 = − 2K & nbsp; K2 − 2 ＞ 0, x1x2 = 2k2 − 2 ＞ 0, so K2 − 2 ≠ 0 △ = (2k) 2 − 8 (K2 − 2) ＞ 0 − 2kk2 − 2 ＞ 02k2 − 2 ＞ 0. The value range of K is - 2 ＜ K ＜ 2, so a

The law of sign change when removing brackets
For example, X-2 (1-2x + x power) + (- 2 + 3x-x power)

Before the bracket is a plus sign, the bracket is removed directly; before the bracket is a minus sign, every item in the bracket becomes the opposite number

If a > 1, b > 1, log2b × log2a = 16, then the minimum value of log2 (AB) is____

log2(ab)=log2a+log2b
>=2 radical (log2a * log2b)
=8

Simplification (a + 3b-3a) (a-2b + 3C)

a^2-2ab+3ac+3ab-6b^2+9bc-3a^2+6ab-9ac=-2a^2-6b^2-ab+9bc-6ac

What are the symbols of mathematical set?

Include to be included: & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 8838; & nbsp; & nbsp; & nbsp; 8839; & nbsp; & nbsp; & nbsp; 8834; & nbsp; & nbsp; & nbsp; & nbsp; 8835; & nbsp;
For a complete set of collective symbols, please refer to the picture

What is the correct pronunciation of excitement?

[x ī ng f è n] excited

It is known that f is the right focal point of hyperbola C: x ^ 2 - (y ^ 2) / 3 = 1, the intersection of straight line C passing through F with a and B, the intersection of right collimator of circle with diameter a and B with m, N, and the length of inferior arc Mn is p, then p / | ab | =?

If AB is perpendicular to the x-axis, bring x = 3 into y = ± 3, draw a circle with F as the center and radius of 3, and get the angle NFM