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a. ,. 1. 1. 4 r. 4 r. r + 3. r + 3. 4 r = 2 2 r. 10 r 2. 10 r 2. LCM = 2 r 2 5 r = 20 r 2. 10 r 2 = 2 5 r r. ANSWER. The LCD of and is 20 r 2. EXAMPLE 2. Find the LCD of rational expressions. Find the LCD of the rational expressions.
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a. , 1 1 4r 4r r + 3 r + 3 4r = 22r 10r2 10r2 LCM = 2 r2 5 r= 20r2 10r2 = 25rr ANSWER The LCD of and is 20r2. EXAMPLE 2 Find the LCD of rational expressions Find the LCD of the rational expressions. SOLUTION a. Find the least common multiple (LCM) of 4rand 10r2. The common factors are circled.
3x + 4 3x + 4 5 5 b. Find the least common multiple (LCM) of (x – 3)2 b. , x2 – x – 6 x2 – x – 6 (x – 3)2 (x – 3)2 and x2 – x – 6. (x – 3)2 = (x – 3)(x – 3) x2 – x – 6 = (x – 3)(x + 2) LCM = (x – 3)(x – 3) (x + 2)= (x – 3)2(x + 2) ANSWER The LCD of and is (x – 3)2(x + 2). EXAMPLE 2 Find the LCD of rational expressions Find the LCD of the rational expressions. SOLUTION
c. Find the least common multiple ofc – 2and2c + 7. c + 8 c + 8 3 3 Because c – 2 and 2c + 7 cannot be factored, they don’t have any factors in common. The least common multiple is their product, (c – 2)(2c + 7). c. , 2c + 7 2c + 7 c – 2 c – 2 ANSWER The LCD of and is (c – 2)(2c + 7). EXAMPLE 2 Find the LCD of rational expressions Find the LCD of the rational expressions. SOLUTION
1 1 m + 1 m + 1 3. , 4. , 28m 28m 7m3 7m3 2 2 x2 +2 x2 +2 x2 + 4x – 5 x2 + 4x – 5 x2 + 7x + 10 x2 + 7x + 10 ANSWER ANSWER The LCD of and is 28m3. The LCD of and is (x +5)(x – 1)(x + 2). for Example 2 GUIDED PRACTICE Find the LCD of the rational expressions.
a + 6 a + 6 5a 5a a – 4 a – 4 a + 3 a + 3 5. , ANSWER The LCD of and is (a +3)(a – 4). for Example 2 GUIDED PRACTICE Find the LCD of the rational expressions.