The correct answer is: [A]: " y³ + 27 " .
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Explanation:
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(y + 3) (y² − 3y + 9) =
y*y² = y³
-3y *y = − 3y²
+9*y = + 9y
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= (y³ − 3y² + 9y) ;
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+3*y² = + 3y²
-9*y = − 9y
(+3)*(+9) = + 27
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= (3y² − 9y + 27) ;
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→ (y + 3) (y² − 3y + 9) =
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(y³ − 3y² + 9y) + (3y² − 9y + 27) =
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y³ − 3y² + 9y + 3y² − 9y + 27 = ?
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Combine the "like terms":
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y³ ;
− 3y² + 3y² = 0 ; [cancel out] ;
+ 9y − 9y = 0 ; [cancel out] ;
+ 27 ;
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to get:
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" y³ + 27 " ;
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→ which is: Answer choice [A]: " y³ + 27 " .
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