Question

For each pair of expressions below, without substituting in specific values, determine which of the expressions in the given pairs is larger. Explain your reasoning in a sentence or two. If you need to, test with values, but your explanation should explain what's going on without simply describing the values

you plugged in.

Answer 1

1. 5+t²
2. 15/x²
3. it depends (see below)
4. it depends (see below)

Explanation:

1. t² is a positive number. Adding a positive number to 5 will always produce a larger result than subtracting the same positive number from 3. The larger expression is 5+t².

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2. The expressions are only defined for x ≠ 0, so for x² a positive number. For any x, the expressions are both positive. 15/(7x²) is 1/7 of 15/x², so will always be smaller. The larger expression is 15/x².

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3. As in 2, these expressions are only defined for x ≠ 0. One expression is the opposite of the other. A number is greater than its opposite when it is positive, so 1/x > 1/-x for x > 0; and 1/-x > 1/x for x < 0.

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4. The expression (k -6)² has the same range of values as k², but its graph is shifted 6 units to the right. The left branch of (k -6)² will be greater than k² for any k < 3. Similarly, the right branch of k² will be greater than (k -6)² for any k > 3.