Question

Difficulty: MediumEvaluating Algebraic Expressions

Evaluate the algebraic expression 3x22xy+y23x^2 - 2xy + y^2 for x=3x = -3 and y=2y = -2.

Answer:The value of the expression 3x22xy+y23x^2 - 2xy + y^2 when x=3x = -3 and y=2y = -2 is 【19】.

Answer

19
Substituting x=3x = -3 and y=2y = -2 into 3x22xy+y23x^2 - 2xy + y^2 yields 3(3)22(3)(2)+(2)2=3(9)12+4=2712+4=193(-3)^2 - 2(-3)(-2) + (-2)^2 = 3(9) - 12 + 4 = 27 - 12 + 4 = 19.

Step-by-Step Solution

1
Substitute x=3x = -3 and y=2y = -2 into the expression
3(3)22(3)(2)+(2)23(-3)^2 - 2(-3)(-2) + (-2)^2
Replace each variable with its assigned value, using parentheses to properly preserve negative signs.
2
Evaluate the exponent terms
3(9)2(3)(2)+43(9) - 2(-3)(-2) + 4
Follow the order of operations (PEMDAS) by evaluating powers first: (3)2=9(-3)^2 = 9 and (2)2=4(-2)^2 = 4.
3
Perform the multiplications
2712+427 - 12 + 4
Multiply the numerical factors: 3×9=273 \times 9 = 27 and 2×(3)×(2)=12-2 \times (-3) \times (-2) = -12.
4
Perform addition and subtraction from left to right
1919
Subtract 1212 from 2727 to get 1515, then add 44 to arrive at 1919.

Key Concept

Evaluating Algebraic Expressions with Negative Values
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