Question

Difficulty: HardEvaluating Algebraic Expressions
If p=−3p = -3, q=12q = \frac{1}{2}, and r=−27r = -27, what is the value of the algebraic expression below?
p2q−3+r1/3(2pq+5)2+q−1\frac{p^2 q^{-3} + r^{1/3}}{(2pq + 5)^2 + q^{-1}}

Answer: 11.5

Answer

11.5
Evaluating each component of the expression step-by-step using order of operations:
1. Numerator: p2q−3+r1/3=(−3)2(12)−3+(−27)1/3=9⋅8+(−3)=72−3=69p^2 q^{-3} + r^{1/3} = (-3)^2 \left(\frac{1}{2}\right)^{-3} + (-27)^{1/3} = 9 \cdot 8 + (-3) = 72 - 3 = 69.
2. Denominator: (2pq+5)2+q−1=(2(−3)(12)+5)2+(12)−1=(−3+5)2+2=22+2=4+2=6(2pq + 5)^2 + q^{-1} = \left(2(-3)\left(\frac{1}{2}\right) + 5\right)^2 + \left(\frac{1}{2}\right)^{-1} = (-3 + 5)^2 + 2 = 2^2 + 2 = 4 + 2 = 6.
3. Final Quotient: 696=11.5\frac{69}{6} = 11.5.

Step-by-Step Solution

1
Evaluate the terms in the numerator
Numerator = 69
Since p=−3p = -3, p2=9p^2 = 9. With q=12q = \frac{1}{2}, q−3=23=8q^{-3} = 2^3 = 8. Thus, p2q−3=9⋅8=72p^2 q^{-3} = 9 \cdot 8 = 72. Also, r1/3=(−27)1/3=−3r^{1/3} = (-27)^{1/3} = -3. Adding these values gives 72+(−3)=6972 + (-3) = 69.
2
Evaluate the terms in the denominator
Denominator = 6
First, 2pq=2(−3)(12)=−32pq = 2(-3)\left(\frac{1}{2}\right) = -3. Then (2pq+5)2=(−3+5)2=22=4(2pq + 5)^2 = (-3 + 5)^2 = 2^2 = 4. Next, q−1=(12)−1=2q^{-1} = \left(\frac{1}{2}\right)^{-1} = 2. Adding these components gives 4+2=64 + 2 = 6.
3
Divide the numerator by the denominator
11.5
Dividing the numerator (69) by the denominator (6) yields 696=11.5\frac{69}{6} = 11.5 (or 232\frac{23}{2}).

Key Concept

Evaluating algebraic expressions with negative bases, negative exponents, fractional exponents, and order of operations.
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