How to calculate simply by 8 times bracket, 125 times 9 times bracket

How to calculate simply by 8 times bracket, 125 times 9 times bracket

8×﹙125×9﹚＝﹙8×125﹚×9＝1000×9＝9000

Given the quadratic function f (x), when x = 1 / 2, there is a maximum value of 25. When f (x) = 0, the cubic sum of two real number roots is 19, find f (x)

Let f (x) = ax ^ 2 + BX + C, and the two roots are X1 and X2, then X1 ^ 3 + x2 ^ 3 = 19, that is, (x1 + x2) ((x1 + x2) ^ 2-3x1x2) = 19. When the function takes the extremum, its derivative is equal to 0 (if you haven't learned, remember to take the maximum or minimum, x = - B / 2a), that is, when x = 1 / 2, 2aX + B = 0, and the solution is b = - A, because X1 + x2 = - B / a (root

The price of a commodity is 200 yuan. Affected by the financial crisis, the price of a commodity is 200 yuan after two consecutive price cuts of 20%_____ .
(A) 114 yuan (b) 120 yuan (c) 128 yuan (d) 144 yuan (E) 160 yuan

200 × (1-20%) × (1-20%) = 128 yuan
Choose C

Let the domain of definition of function y = f (x) be r, and f (X-Y) = f (x) - f (y), f (2) = 1 (1) to find F
Let y = f (x) be defined as R, and f (X-Y) = f (x) - f (y), f (2) = 1
(1) Find the value of F (0);
(2) Judging the parity of function;
(3) If f (x) + F (2 + x) < 2, find the range of X

A:
The definition field of F (x) is r, satisfying f (X-Y) = f (x) - f (y), f (2) = 1
1) Let x = y have: X-Y = 0
f(0)=f(x-y)=f(x)-f(x)=0
f(0)=0
2) Let x + y = 0 have y = - X
f(0)=f(x+y)=f[x-(-y)]=f(x)-f(-y)=f(x)-f(-x)=0
So: F (- x) = - f (x)
So: F (x) is an odd function
3）f(x)+f(2+x)

The English mathematical expressions round to and round off are all "rounded" in Chinese translation. Is there any difference between them?

Generally speaking, round to is rounded
and
Round off means to convert to an integer, that is, without a decimal point

The price of a product was raised by 10% at first and then decreased by 10%. What's the price now?
I still don't understand
If you can, please write out the process!
3Q!
How to ask

（1+10％）×（1-10％）＝99％

Given | a + B + Z | + (AB-1) ^ 2 = 0, find the value of 2 (a + b) - 2 [AB + (a + b)] - 3 [2 (a + b) - 3AB]

|a+b+z|+(ab-1)^2=0
Because both terms on the left side of the equation are greater than or equal to 0
The right side of the equation is 0
So a + B + Z = 0, AB-1 = 0
a+b=-z
ab=1
2(a+b)-2[ab+(a+b)]-3[2(a+b)-3ab]
=2(a+b)-2(a+b)-2ab-6(a+b)+9ab
=-6(a+b)+7ab
=-6z+7

If (1 / M) + (n / 1) = (7 / M + n), what is the value of (n / M) + (M / N)

From the meaning of the title
（m+n)/mn=7/m+n
(m+n)^2=7mn
That is m ^ 2 + n ^ 2 + 2Mn = 7mn
m^2+n^2=5mn
Original formula = n / M + m / N = (m ^ 2 + n ^ 2) / Mn = 5MN / Mn = 5

A commodity is priced at 20% and then sold at 80% of the price. As a result, each commodity loses 64 yuan. What is the cost of this commodity?

Design cost X Yuan
（x+20%x）*80%=x-64
The answer is 1600

The following numbers are expressed by scientific notation: (1) 467.2 (2) 6000.3

（1）4.672×10²
（2）6.0003×10³