Solve the system by substitution. -4x + 8y = 56 x + 7y = 49
A. No solution
B. (0, 7)
C. (1, 6)
D. (-7, 0)
Answer: B
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Find the derivative of the function.r = (sec ? + tan ?)-2
A. -2(sec ? + tan ?)-3
B. 
C. -2(sec ? tan ? + sec2?)-3
D. -2(sec ? + tan ?)-3(tan2 ? + sec ? tan ?)
Find a general expression for the slope of a tangent line to the indicated curve.y = 8 - 8x3
A. 8 - 24x2 B. -24x2 C. -24x3 D. 8 - 8x2
Combine and simplify, if possible.7
+ 8
A. 31
B. 15
C. -31
D. 17
Solve the problem.In a Psychology class, the students were tested at the end of the course on a final exam. Then they were retested with an equivalent test at subsequent time intervals. Their average scores after t months are given in the table.
Using a graphing utility, fit a logarithmic function y = a + b ln x to the data. Using the function you found, estimate how long will it take for the test scores to fall below 84%. Express your answer to the nearest month.
A. 8 months B. 12 months C. 20 months D. 10 months