Question

Difficulty: MediumEvaluating Algebraic Expressions

Calculate the exact value of the algebraic expression 3x2y−12yx3x^2y - \frac{12y}{x} when the variables are assigned the values x=−2x = -2 and y=−5y = -5.

Answer: -90

Answer

The correct evaluated result is -90.
By accurately substituting the values, correctly squaring the negative number (−2)2=4(-2)^2 = 4, evaluating the fractional term as −60−2=30\frac{-60}{-2} = 30, and completing the final subtraction −60−30-60 - 30, the expression correctly evaluates to -90.

Step-by-Step Solution

1
Substitute the given variable values into the algebraic expression.
3(−2)2(−5)−12(−5)−23(-2)^2(-5) - \frac{12(-5)}{-2}
This sets up the expression with numerical values for evaluation.
2
Evaluate the exponent applied to the negative base.
(−2)2=4(-2)^2 = 4, making the expression 3(4)(−5)−12(−5)−23(4)(-5) - \frac{12(-5)}{-2}
According to the order of operations (PEMDAS), exponents must be evaluated before multiplication and division.
3
Perform the multiplication in the first term.
3(4)(−5)=12(−5)=−603(4)(-5) = 12(-5) = -60
Evaluating the first term completely from left to right.
4
Perform the multiplication and division in the second term (the fraction).
12(−5)−2=−60−2=30\frac{12(-5)}{-2} = \frac{-60}{-2} = 30
Evaluating the fractional term by first multiplying the numerator, then dividing by the negative denominator.
5
Subtract the result of the fraction from the first term.
−60−30=−90-60 - 30 = -90
The final operation is the subtraction of the two evaluated terms.

Key Concept

Evaluating algebraic expressions using substitution and the order of operations with signed numbers.
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