I bought 150 story books and a batch of science and technology books. The number of science and technology books is 25 less than 1.2 times of story books. How many science and technology books did the school buy?

Set up x books of science and technology
1.2*150-25=x
180-25=x
155=x
A: the school bought 155 science and technology books

There are 150 story books and science and technology books. Story books are five times as many as science and technology books. How many story books and science and technology books are there

Solution: suppose there are x science and technology books, then the story books are 5x
X＋5X=150
6X=150
X=25
5X=5×25=125
Arithmetic method: Science and technology book 150 (5 + 1) = 25 (copies)
Storybook 25 × 5 = 125

(- A's third power × B's second power) ABC
Why not (- A's third power × a) (- A's third power × b) (- A's second power × C) (B's second power × a) (B's second power × b) (B's second power × C)? But the fourth power of - a × the third power of B × C?
The responder should be patient, or he will be bored to death

This belongs to the problem of priority. In arithmetic operation, multiplication and division is prior to addition and subtraction. For example, a + b * C should calculate b * C first, and then add the result to A. but in this problem, only multiplication operation appears. It's OK to calculate the numbers on both sides of the multiplication sign first

As shown in the figure, P is a point on the vertical bisector of line AB, and M is a point on line AB which is different from a and B, then the size relationship of PA, Pb and PM is PA_ PB _ PM．

∵ P is a point on the vertical bisector of line AB, ∵ PA = Pb; ∵ m is the point on line AB which is different from a and B, ∵ according to Pythagorean theorem, PA > PM

Y-1 = 3 (y + 1) x + 5 / 6 = 1 X-2 3x - (x + 5) = - 3 10-4 (x-3) = 2 (x-1) 5x-2 (4x-3) - 12 = 0
13-3(x-2)=2(x+1) 15x-5(x-1)=105-3(x+8)

y=-2
x=-17/3
x=1
x=4
x=-2
x=17/5
x=76/13

The distance from the top of the cone to any point of the circumference of the bottom circle is 6cm, and the bottom radius is 1cm. Surface area!

S=πr*r+1/2*6*2πr=7π
Base area = π R * r
Side area = 1 / 2 * perimeter of bottom circle (2 π R) * bus length (6)

From minus 52, add one by one to get a series of integers minus 52, minus 51, minus 50. (1) what's the hundredth integer
(2) What is the sum of these 100 integers

1. This is an arithmetic sequence. Obviously, the 100th number is 99 larger than the first number, that is, the 100th number = - 52 + 99 = 47
2. And S = (- 52 + 47) + (- 51 + 46) + (a total of 50 groups)
＝-5 X 50
＝-250

Given the equation x ^ 2 + y ^ 2 = 2 of circle O and the equation x ^ 2 + y ^ 2-8x + 10 = 0 of circle O1, the tangent lengths from the moving point P to circle O and circle O1 are equal,
Then the trajectory equation of the moving point P is

The tangent length is equal, that is, the square of the distance from the point to the two centers is equal to the square of the radius
So: P = (x, y)
X ^ 2 + y ^ 2 = 2, Center (0,0)
x^2+y^2-8x+10=0
x^2-8x+16+y^2=6
(x-4) ^ 2 + y ^ 2 = 6, Center (4,0)
(x^2+y^2)-2=((x-4)^2+y^2)-6
-2=16-8x-6
x=3/2
So: the trajectory equation of the moving point P is x = 3 / 2

What are the grouping methods for factoring a4-a3 + A-1

Original formula = A & # 179; (A-1) + (A-1)
=(a-1)(a²+1)
=(a-1)(a+1)(a²-a+1)

4X + 3Y = 16, 6x-5y = 33 to solve the system of inequalities

4X + 3Y = 16 two sides at the same time * 3 get 12x + 9y = 48
6x-5y = 33, both sides * 2 at the same time, we get the formula 12x-10y = 66
If you subtract two from one, you get 19y = - 18, y = - 18 / 19, and then bring it in to get x = 179 / 38

I bought 150 story books and a batch of science and technology books. The number of science and technology books is 25 less than 1.2 times of story books. How many science and technology books did the school buy?