Xiaojun's original storybooks are three times as many as Xiaoli's. Xiaojun bought seven more. After Xiaoli bought six, Xiaojun's books are twice as many as Xiaoli's?

Xiaojun's original storybooks are three times as many as Xiaoli's. Xiaojun bought seven more. After Xiaoli bought six, Xiaojun's books are twice as many as Xiaoli's?

Suppose: Xiao Li had x books, but Xiao Jun had 3x
So after buying books later, 3x + 7 = 2 &; (x + 6)
3X+7=2X+12 X=5 3X=15
A: Xiaoli had 5 books and Xiaojun had 15

Xiao Jun has read 48 pages of a story book. At this time, the ratio of the number of pages he has read to the number of pages he has not read is 3:5. How many pages are there in this story book?

A: this story book has 128 pages

Xiao Jun read a story book. On the first day, he read one sixth of the book. On the second day, he read 42 Pages
How many pages is the book?

With X page, the meaning of the title is x / 6 + 42 = 3x / 5, and the solution is x = 180

When Xiao Ming read a story book, he had read 55 pages, 9 more than the number of pages he had not read, and how many percent more than the number of pages he had not read? (reserve one before the percent sign.)
Keep one decimal place before the percent sign

9/（55-9)*100%=19.6%
19.6% more pages seen than not seen

Use group decomposition method. If other formula method is needed, it can be used. The premise must be group decomposition method
1.2xy-x²+1-y²
2.5ax+56x+3ay+3by
3.x^3-x²+x-1
4.x²-x-y²-y
5.18a²-32b²-18a+24b
6.x²-25+y²-2xy
7.y^4-4y^3+4y²-1
8.4a²-b²-4c²+4bc
9.x²-y²+ax+ay
10.a+b+ab+1
11.a²-ab+ac-bc
12.7x²+3y+xy+21x
13.2ac-6ad+bc-3bd

1.2xy-x²+1-y²=1-（x²-2xy+y²）=1-（x+y）²=（1+x+y）*（1-x-y）2.5ax+5bx+3ay+3by=a*（5x+3y）+b*（5x+3y）=（5x+3y）*（a+b）3.x^3-x²+x-1=x²（x-1）+x-1=（x-1）*（x²+1...

1. It is known that the quadratic function f (x) = x squared two - 2x + 2. When x = x, f (x) has a minimum value of
2. Given the quadratic function f (x) = - x squared two + 4x + 2, when x =, f (x) has the maximum value of

(1) F (x) = x & sup2; - 2x + 2 = x & sup2; - 2x + 1 + 1 = (x-1) & sup2; + 1 when x = 1, the minimum value of F (x) is 1 (2) f (x) = - X & sup2; + 4x + 2 = - X & sup2; + 4x - 4 + 6 = (x - 2) & sup2; + 6, so when x = 2, the maximum value of F (x) is 6

The number of intersections between the straight line y = 2x + 1 and the parabola y = x & # 178; - 3x + 1

y=2x+1
y=x²-3x+1
The results are as follows
.

If the symmetry axis of the parabola is parallel to the Y axis, the vertex coordinates "3, - 1" pass through the points "0, - 4",

Vertex type
The vertex is (3, - 1)
Let this parabola be
y=a(x-3)^2-1
Over point (0, - 4)
Substituting
－4＝a(0-3)^2-1
a=-1/3
therefore
y=－1/3（x-3)^2-1
＝－1/3x^2＋2x-4

Party A and Party B are going towards each other from a and B at the same time. The first time they meet is 60km away from A. after meeting, they continue to advance at the same speed and return immediately after arriving at B and A. on the way, they meet for the second time. The meeting point is 40km away from A. how many kilometers is the distance between a and B

Let AB be x km apart
60/(x-60)=(2x-40)/(x+40)
The solution is x = 110 km

Given Q (2,0) in rectangular coordinate system and circle x + y = 1, the ratio of tangent length and MQ from moving point m to circle C is equal to root 2, and the trajectory equation of M is obtained
Can you explain why? How

If the square of the tangent length from the moving point m (x, y) to the circle C = the square of the distance from the moving point m to the center of the circle C - R & # 178;, then:
Tangent length d = √ [MC & # 178; - R & # 178;]
d：|MQ|=√2
d=√2|MQ|
d²=2|MQ|²
(x²＋y²)－1=2×[(x－2)²＋y²]
The results are as follows
x²＋y²－8x＋9=0
This is the trajectory equation of the moving point M