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Unformatted text preview: tiply by 100 to clear decimals. 2(x – 2) = 100 2x – 4 = 100 2x = 104 x = 52 5. (A) 4x + 4r = 2x + 10r 2x = 14r x = 7r (D) An even number of negative signs gives a positive product. 6 × 4 × 4 × 2 = 192 3.
= –10 5 (A) 4. 5. (B) (A) +4 + 0 + ( –1) + ( –5) + ( –8) 5 5(–2) – 4(–10) – 3(5) = –10 + 40 – 15 = +15 www.petersons.com 130 Chapter 8 Exercise 3
1. (C) Multiply first equation by 3, then add. 3x – 9y = 9 2x + 9y = 11 5x = 20 x=4 Multiply each equation by 10, then add. 6x + 2y 5x – 2y 11x x 3. = 22 = 11 = 33 =3 Exercise 4
1. (B) (x – 10) (x + 2) = 0 x – 10 = 0 x = 10 or –2 2. (B) x+2=0 (5x – 2) (5x + 2) = 0 5x – 2 = 0
2 2 x= or – 5 5 2. (B) 5x + 2 = 0 3. (D) 6x(x – 7) = 0 6x = 0 x = 0 or 7 x–7=0 (B) Multiply first equation by 3, second by 2, then subtract. 6x + 9y = 36b 6x – 2y = 14b 11y = 22b y = 2b 4. (E) (x – 16) (x – 3) = 0 x – 16 = 0 x = 16 or 3 x–3=0 5. (D) x2 = 27 x = ± 27 4. (A) 2x – 3y = 0 5x + y = 34 But 27 = 9· 3 =3 3 Multiply first equation by 5, second by 2, and subtract. 10x – 15y 10x + 2y –17y y 5. (B) =0 = 68 = –68 =4 Therefore, x = ±3 3 Subtract equations. x+y x–y 2y y = –1 =3 = –4 = –2 www.petersons.com Concepts of Algebra—Signed Numbers and Equations 131 Exercise 5
1. (C)
2y = 4 Retest
1. 2. (D) (–3) + (+7) – (–5) = (+9) 2y = 16 y=8 (D) An odd number of negative signs gives a negative product.
2 1 1 2 – ( –4 )(+ 12 ) – 6 = –4 2 Checking, 16 = 4, which is true. 2. (D) 4 2 x – 1 = 12
2x – 1 = 3 2x – 1 = 9 2x = 10 x=5 3. (D) The sum of (–4) and (–5) is (–9). The
1 1 is – . 27 3 product of 9 and –
–9 1 – = +27 3 Checking, 4 9 = 12, which is true. 3. (E) x2 – 35 = 25 – 10x + x2 –35 = 25 – 10x 10x = 60 x=6 4. (B) 7b + 5d = 5x – 3b 10b + 5d = 5x x = 2b + d Checking, 1 = 5 – 6, which is not true. 4. (B) 18 = 3 2 y 6 = 2y 36 = 2y y = 18 Checking 26 = 3 36 + 8, 26 = 3(6) + 8, which is true. 5. (D) Multiply first equation by 3, second by 2, then...
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This note was uploaded on 08/15/2010 for the course MATH a4d4 taught by Professor Colon during the Spring '10 term at EmbryRiddle FL/AZ.
 Spring '10
 Colon
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