Each fairy tale book costs 10 yuan. Lingling pays 100 yuan to get () fairy tale books

Each fairy tale book costs 10 yuan. Lingling pays 100 yuan to get () fairy tale books

Each fairy tale book is 10 yuan, buy 5 free 1. Lingling pay 100 yuan, a total of (12) fairy tale books
The actual price of each book is 5 * 10 / 6 yuan for 5 copies, so 100 yuan can buy 12 copies for 100 / (5 * 10 / 6)

Lily has 10 storybooks. After taking half of the fairy tale books, there are still seven. How many fairy tale books does lily have?

(10-7) multiply by 2 equals 6

Compare the square of real number x with the size of X

Discussion by situation
If x = 0 or 1, X & # 178; = X
If 0 ﹤ x ﹤ 1, X ﹤ 178; ﹤ x
If x > 1, X & # 178; > X
If x < 0, X & # 178; > X

Help me solve the equation 30 + 2Y = 120. Y=

30+2Y=120
2y=120-30
2y=90
y=90\2
y=45

The volume formula of triangle

How can a triangle have volume?

Given cosa = one third, cos (a + b) = 1, how to prove the solution of COS (2a + b) = one third

cosa=1/3,sina=2√2/3,
cos(a+b)=1,sin(a+b)=0
cos(2a+b)=cos[(a+b)+a]=cos(a+b)cosa-sin(a+b)sina=1/3

Solution ratio: 5 / 8 = 9 / X

5 out of 8 = 9 out of 8
x = 72 /5

Find the maximum and minimum of quadratic function y = 3x ^ 2 + 12x-4 when - 3 ≤ x ≤ 1

Since the quadratic coefficient is positive, the image of the function is a parabola with the opening upward,
The axis of symmetry is x = - 2,
So y is a decreasing function on [- 3, - 2] and an increasing function on [- 2,1]
So when x = - 2, the minimum value of Y is 12-24-4 = - 16;
When x = 1, the maximum value of Y is 3 + 12-4 = 9

When m is chosen, the intersection of y = - 5 / 4x + 1 / 2m + 1 / 4 and y = - 2 / 3x + 1 / 3M is in the fourth quadrant

Y = - 5 / 4x + 1 / 2m + 1 / 4 = (- 5x + 2m + 1) / 4Y = - 2 / 3x + 1 / 3M = (- 2x + m) / 3 is substituted to get: (- 5x + 2m + 1) / 4 = (- 2x + M) / 33 (- 5x + 2m + 1) = 4 (- 2x + m) - 15x + 6m + 3 = - 8x + 4m7x = 2m + 3x = (2m + 3) / 7 > 0m > - 3 / 2 substituting x = (2m + 3) / 7 into y = (- 2X + m) / 3 to get y = (- 2 (2m + 3) / 7 + m) / 3 = (- 2 (2m + 3)

Calculation: 2 * 4 / 1 + 4 * 6 / 1 + 6 * 8 / 1 +... 48 * 50 / 1 =?

2 * 1 / 4 + 4 * 1 / 6 + 6 * 1 / 8 +... 48 * 1 / 50
=1/2[(1/2-1/4)+(1/4-1/6)+(1/6-1/8)+...+(1/48-1/50)]
=1/2[1/2-1/50]
=12/50
=6/25