Over Lesson 2–2 A.A B.B C.C D.D 5-Minute Check 1 A.–7 B.–1 C.1 D.7 Find –4 + (–3). Find – A.–34 B.–6 C.6 D.34 Find 2 + (–6) + 9. A.–5 B.5 C.–17 D.17

Splash Screen

Then/Now You have already learned to subtract integers using algebra tiles. (Explore 2–3) Subtract integers. Evaluate expressions containing variables.

Concept In other words, change the subtract sign to addition and change the sign of the number after the subtraction sign (we say “add the opposite!”)

Example 1 Subtract a Positive Integer A. Find 9 – – 14= 9 + (–14)To subtract 14, change to add –14. = –5Simplify. Answer: –5

Example 1 B. Find –10 – 8. –10 – 8= –10 + (–8) To subtract 8, change to add –8. = –18 Simplify. Answer: –18 Subtract a Positive Integer

A.A B.B C.C D.D Example 1 A.2 B.–2 C.–3 D.14 A. Find 6 – 8.

A.A B.B C.C D.D Example 1 A.–22 B.–4 C.4 D.22 B. Find –9 – 13.

Example 2 Subtract a Negative Integer A. Find 15 – (–4). 15 – (–4)= To subtract –4, change to add 4. = 19Simplify. Answer: 19

Example 2 B. Find –11 – (–7). –11 – (–7)= –11 + 7To subtract –7, change to add 7. = –4Simplify. Answer: –4 Subtract a Negative Integer

A.A B.B C.C D.D Example 2 A.6 B.10 C.–6 D.16 A. Find 8 – (–2).

A.A B.B C.C D.D Example 2 A.17 B.7 C.–17 D.–7 B. Find –12 – (–5).

Example 3 Subtract a Negative Integer WEATHER The wind makes the outside temperature feel colder than the actual temperature. How much colder does a temperature of 0°F with a 20-mile-per-hour wind feel than the same temperature with a 10-mile-per-hour wind? UnderstandYou need to find how much colder 0° feels with a 20-mile-per-hour wind than with a 10-mile-per-hour wind.

Example 3 Subtract a Negative Integer PlanSubtract the wind chill temperature at 20 miles per hour from the wind chill temperature at 10 miles per hour. Answer: It feels 6 degrees colder. Solve–22 – (-16)= – To subtract –16, add 16. = –6Add –22 and 16. CheckSince –22 < –16, it makes sense that the temperature is colder.

A.A B.B C.C D.D Example 3 A.5 degrees colder B.7 degrees colder C.8 degrees colder D.10 degrees colder WEATHER How much colder does a temperature of 0° feel with a 30-mile-per-hour wind than the same temperature with a 10-mile-per-hour wind?

Example 4 Evaluate Algebraic Expressions Evaluate x – y + z if x = 4, y = –5, and z = –14. Answer: –5 x – y + z=4 – (–5) + (–14) Replace x with 4, y with –5, and z with –14. =9 + (–14) Use order of operations. =–5Add 9 and –14.

A.A B.B C.C D.D Example 4 A.–12 B.–6 C.6 D.–27 Evaluate m – n if m = –9 and n = –3.

End of the Lesson