What does 9 mean? Is it the factorial of 9?

What does 9 mean? Is it the factorial of 9?

9! Is the double factorial of 9
9!=9*7*5*3*1

If AB is a rational number, define a new operation △: a △ B = 2ab-1, for example, (- 3) △ 4 = 2 × (- 3) × 4-1 = - 25 （1）3△（-5）； （2）[3△（-5）]△（-2）.

(1)3△(-5)
=2 × 3 × (- 5) - 1 (a * b = 2ab-1, the relation between numbers)
= -31
(2)
[3△(-5)]△(-2)
= (-31)△(-2)
= 2 × (-31) × (-2) - 1
= 124 - 1
= 123
I worked out your question through the following questions,
If a / B is a rational number, a new operation "*" a * b = 2Ab + 1 is defined, for example: {3} * 4 = 2 * 4 + 1 = 23. Try to calculate: {1} 3 * {5} {2} {6 * {- 7}

We know two rational numbers ab. define the operation "ා" as a ා B = a + ab. try to find the value of 6 ා [- 5]

It's very simple
6#(-5)
=6+6*(-5)
=6+(-30)
=-(30-6)
=-24

For the rational number AB, define the operation as follows: a ★ B = ab of a + B, find 3 ★ (- 4) Answer with the meaning of the question

A ★ B = (a + b) (AB)
3 ★ (- 4) = (3 + (- 4)) = 12

Given that X and y are rational numbers, if a new operation symbol "*" is specified and X * y = XY + 1 is defined, please complete it according to the meaning of operation symbol "*" The following questions （1）2﹡4 （2）（1﹡4）﹡（-2）

2*4=2×4+1=9
（1*4）*（-2）=（1×4+1）*（-2）=5*（-2）=5×（-2）+1=-9

It is known that X and y are rational numbers. If a new operation is specified with the sign "*", the meaning is x * y = XY + 1. Please complete the operation according to the meaning of this new operation 1) Calculate 2 * 4 (2) Calculate (1 * 4) * - 2 (3) Choose two rational numbers randomly and fill in the following fields respectively. Compare the results of the two operations. What do you find? Please write your findings on the straight line below: □ * and * * * . (4) Please follow the method in (3) to explore the relationship between a * (B + C) and a * B + b * C, and express this relationship by equation

(1) 2 * 4 = 2 × 4 + 1 = 9 (2) (1 * 4) * (- 2) = (1 × 4 + 1) × (- 2) + 1 = - 9 (3) randomly choose two rational numbers and try to find □ * 0 = ≡ because □ * 0 = □×× + 1 = 0 × □. (4) the title is wrong

x. Y is a rational number. Now a new operation symbol * is defined, X * y = 2xy-1. Please calculate (1 * 3) * - 2)

x*y=2xy-1,
(1*3)*(-2)
=(2×1×3-1)*(-2)
=5*(-2)
=2×5×(-2)-1
=-20-1
=-21

The operation "*" is defined in the set of rational numbers, and its rule a * b = A / 2-b. try to find the solution of (x * 3) * 2 = 1

0

0

(x*3)*2=(x-3)*2=x-3-2=1
X=6

Let a and B be rational numbers. If the operation symbol ＊ is defined as a ＊ B = the square of a - the square of B + A + 2B, when what is the value of X, the value of formula x ＊ - 2 is 19?

x²-(-2)²+x+2(-2)＝19
x²-4+x-4=19
x²+x-27=0
x=(-1±√109)/2