If the equation of motion of a body is s = 7T ^ 2-13t + 8, then its instantaneous velocity at t = () is 1 Note: if the interval is | T, t + △ x |, then △ y = 7 △ x ^ 2 + 14T △ x + 7T ^ 2-13t-13 △ x + 8-7t ^ 2 + 13t-8 = 7 △ x ^ 2 + 14T △ x, then △ Y / △ x = 7 △ x + 14T, so 14T = 1, t = 1 / 14. But the answer is 1?

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• 1. A math problem of Liberal Arts in senior two. (Application of derivative) A manufacturer manufactures and sells a kind of beverage in spherical bottles. The manufacturing cost of the bottle is 0.8 π R ^ 2, where R is the radius of the bottle, and the unit is cm. It is known that the manufacturer can make a profit of 0.2 points for every 1ml of beverage sold, and the maximum radius of the bottle that the manufacturer can manufacture is 6cm Q: (1) what is the radius of the bottle to maximize the profit of each bottle? (2) When the bottle radius is large, the profit of each bottle is the smallest? Please write the process, thank you
• 2. It is known that the derivative of F (x) is 2x ^ 2-4ax-3. If f (x) has and only has one extreme point in (- 1,1), the value range of a is obtained
• 3. Find the sum of all integer solutions of the system of inequalities 5 ＞ 2 (1 − x) − 13X ≤ 23 − X
• 4. Solve the system of inequalities x + 1 ＞ 0. X ≤ (X-2 / 3) + 2, and write the largest integer solution of the system of inequalities
• 5. In the "beautiful Urumqi" activity, a community decided to use 9000 pots of chrysanthemum and 8100 pots of sunflower with a and B gardening styles, a total of 100 flowers were placed in the community. The flowers required for each gardening style are shown in the following table: & nbsp; & nbsp; need chrysanthemum (pot) need sunflower (pot) & nbsp; a shape & nbsp; & nbsp; 100 & nbsp; 60 & nbsp; A B shape & nbsp; 80 & nbsp; Based on the above information, let's set X horticultural models of type A to answer the following questions: (1) please write out the inequalities that meet the meaning of the problem and find out the solution set; (2) if the cost of matching a horticultural model of type A is 600 yuan and that of matching a horticultural model of type B is 800 yuan, try to determine how many of the models of type a can make the cost of the 100 horticultural models the lowest
• 6. Inequalities and systems of inequalities A rectangular football field is xcm in length and 70m in width. If its perimeter is greater than 350m and its area is less than 7560m2, the value range of X is obtained
• 7. If the inequality system 3x − 1 ≥ a + 12 − x > 1 − 2A has no solution, then the value range of a is______ ．
• 8. Inequality and inequality group mathematical problems In a competition, a shooter hits 54 rings in the first six shots. If he wants to break the record of 91 rings (10 times), how many rings can he have in the seventh shot? (2) if the seventh shot is 8 rings, how many times must he hit 10 rings in the last three shots to break the record? (3) if the seventh shot is 10 rings, Do you have to hit 10 rings at least once in the last three shots to break the record?
• 9. Mathematical problems of inequality group The price and quantity of goods bought by the two stores are the same. Store a: after purchasing 200 yuan goods, you can apply for a 20% discount card, and later you can enjoy a 20% discount when purchasing goods; store B can apply for a 10% discount card when purchasing 100 yuan goods, and later you can enjoy a 10% discount when purchasing goods At the beginning, we need to use the system of inequalities to solve the problem, not to discuss it by classification,
• 10. A mathematical problem of inequality in senior one If two angles a and B satisfy - π / 2
• 11. The limit of ((3x + 1) / (3 + x)) ^ (1 / (x-1)) when x tends to 1
• 12. . = = Lim 1 / (x ^ 2-3x + 2) find the limit value,
• 13. If x2-3x + 1 = 0, the value of fraction x2 / (x ^ 4 + x2 + 1) is Ask God for help!
• 14. How many real roots of equation 2x ^ 2-6x / (x-3) = x + 5
• 15. If the set a {x | x + A / x2-4 = 1} is a single element set, then the value set of a is m= The teacher's answers were 2, - 2, - 17 / 4, but I wrote - 17 / 4 and - 4, X + a divided by the square of x minus 4 equals 1
• 16. Given a = {(x, y) | x2 + y2-6x-8y + 20 = 0}, B = {(x, y) | kx-y-4k + 3 = 0}, then the number of elements of a ∩ B is () A. 0B. 1C. 2D. 3
• 17. If M = {y | y = x2 + 1}, n = {y = | y = 3-x2}, then M intersects n =?
• 18. Set a = {y | X & # 178; + 2x, - 2 ≤ x ≤ 2} B = {x | X & # 178; + 2x-3 ≤ 0} take any element a in set a, then what is the probability that a belongs to B Eager for answers
• 19. Set a = {y | y = x & # 178; - 1, X ∈ r}, B = {y | y = - 2x & # 178; + 2, X ∈ r}, find a ∩ B Set a = {y | y = x & # 178; - 1, X ∈ r}, B = {y | y = - 2x & # 178; + 2, X ∈ r}, find a ∩ b set P = {y | y = 3x-1, X & gt; 1}, q = {y | y = - 2x & # 178; + 10, X ∈ r}, find P ∩ Q
• 20. Given the set a = {x │ - 1 ≤ x ≤ 2}, B = {y │ y = 2x-a, a ∈ R, X ∈ a}, C = {Z │ z = x & # 178;, X ∈ a} Is there a real number a so that C is included in B? If it exists, find out the value range of A. if it does not exist, explain the reason.