Which term best describes a proof in which you assume the opposite of what you want to prove?

a. proof by syllogism

b. proof by converse

c. proof by contrapositive

d. proof by contradiction

Describe in detail how you would construct a 95% confidence interval for a set of 30 data points whose mean is 20 and population standard deviation is 3. be sure to show that you know the formula and how to plug into it. also, clearly state the margin of error.

Gabriel determined that his total cost would be represented by 2.5x + 2y – 2. his sister states that the expression should be x + x + 0.5x + y + y – 2. who is correct? explain.

Ellen makes and sells bookmarks. she graphs the number of bookmarks sold compared to the total money earned. why is the rate of change for the function graphed to the left?