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question:A driver would have reduced the time it took to drive from home to the store by 1/3 if the average speed had been increased by 18 miles per hour. What was the actual average speed, in miles per hour, when the driver drove from home to the store?

answer:Let's denote the actual average speed as ( v ) miles per hour and the actual time taken to drive from home to the store as ( t ) hours. The distance from home to the store, therefore, is ( d = vt ). If the driver had increased the average speed by 18 miles per hour, the new speed would be ( v + 18 ) miles per hour. The problem states that by doing so, the time taken would have been reduced by 1/3, so the new time taken would be ( frac{2}{3}t ). The distance would remain the same, so we can set up the equation: [ d = vt = (v + 18) cdot frac{2}{3}t ] Now we can solve for ( v ): [ vt = frac{2}{3}vt + frac{2}{3} cdot 18t ] Divide both sides by ( t ) to get rid of ( t ): [ v = frac{2}{3}v + frac{2}{3} cdot 18 ] Now, let's solve for ( v ): [ v - frac{2}{3}v = frac{2}{3} cdot 18 ] [ frac{1}{3}v = frac{2}{3} cdot 18 ] Multiply both sides by 3 to solve for ( v ): [ v = 2 cdot 18 ] [ v = 36 ] So, the actual average speed when the driver drove from home to the store was boxed{36} miles per hour.

question:Using Horner's method, find the value of the polynomial 7x^3+3x^25x+11 at x=2. A: 69 B: 65 C: 66 D: 67

answer:**Analysis** This problem tests our ability to use Horner's method to compute the value of a polynomial at a given point, focusing on computational skills. It's a fundamental question. **Step-by-step Solution** 1. First, rewrite the given polynomial in the form suitable for Horner's method: f(x) = (((7x+3)x-5)x+11. 2. Substitute the given value x=2 into the rewritten polynomial. 3. Calculate intermediate values: - v_0 = 7 - v_1 = 7 times 2 + 3 = 17 4. Continue the calculations to find the final value of the polynomial: - v_2 = 17 times 2 - 5 = 34 - 5 = 29 - f(2) = 29 times 2 + 11 = 58 + 11 = boxed{69}

question:Given a sequence {a_n} with the sum of its first n terms denoted as S_n, and S_n = 1 a_n. Another sequence {b_n} satisfies b_n = log_4 a_1 + log_4 a_2 + dots + log_4 a_n. 1. Find the general term formula for the sequence {a_n}. 2. Find the sum of the first n terms, denoted as T_n, for the sequence {frac{1}{a_n} + frac{1}{b_n}}.

answer:1. The sum of the first n terms of the sequence {a_n} is S_n, and S_n = 1 - a_n. We can derive that S_{n-1} = 1 - a_{n-1}. By subtracting the two equations, we get 2a_n = a_{n-1}, which means sequence {a_n} is a geometric sequence with a common ratio of frac{1}{2}. Since S_1 = 1 - a_1, the first term is frac{1}{2}. Therefore, the general term formula for the sequence {a_n} is: a_n = frac{1}{2^n} 2. b_n = log_4 a_1 + log_4 a_2 + dots + log_4 a_n = log_4(a_1 a_2 dots a_n) =log_4 left(frac{1}{2}right)^{1+2+3+dots+n} = -frac{n(n+1)}{4}. The general term formula for the sequence {frac{1}{a_n} + frac{1}{b_n}} is: 2^n - frac{4}{n(n+1)} The sum of the first n terms for the sequence {frac{1}{a_n} + frac{1}{b_n}} is: T_n = (2 + 2^2 + 2^3 + dots + 2^n) - 4(1 - frac{1}{2} + frac{1}{2} - frac{1}{3} + dots + frac{1}{n} - frac{1}{n+1}) =frac{2(1-2^n)}{1-2} - 4(1 - frac{1}{n+1}) =2^{n+1} + frac{4}{n+1} - 6. The final answers are: 1. boxed{a_n = frac{1}{2^n}} 2. boxed{T_n = 2^{n+1} + frac{4}{n+1} - 6}

question:Elective 45: Special Topics on Inequalities: If the equation x^24x+|a3|=0 has real roots with respect to x, (Ⅰ) find the set A of values of the real number a (Ⅱ) If for all a in A, the inequality t^22at+12<0 always holds, find the range of values for t.

answer:(Ⅰ) Since the equation x^2-4x+|a-3|=0 has real roots, we have Delta=16-4|a-3| geq 0, which implies |a-3| leq 4, thus -4 leq a-3 leq 4, so -1 leq a leq 7. Therefore, the set of values for the real number a is A={a|-1 leq a leq 7}. (Ⅱ) Since for all a in A, the inequality t^2-2at+12<0 always holds, let f(a)=-2at+t^2+12, then f(a)<0 always holds. Thus, f(-1)<0 and f(7)<0, which gives 2t+t^2+12<0 (1), and -14t+t^2+12<0 (2). Solving (1) gives t in emptyset, and solving (2) gives 3<t<4. In conclusion, the range of values for t is boxed{(3, 4)}.

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