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Problem 8 - Entrance Test
Expand (2x + 3)^3.
A. 8x^3 + 27
B. 8x^3 + 36x^2 + 54x + 27
C. 8x^3 + 12x^2 + 18x + 27
D. 8x^3 + 54x^2 + 36x + 27
Check Answer
Show Solution
Correct: B
Using the identity (a+b)^3 = a^3 + 3a^2b + 3ab^2 + b^3, here a = 2x and b = 3. (2x + 3)^3 = (2x)^3 + 3(2x)^2(3) + 3(2x)(3)^2 + (3)^3 = 8x^3 + 3(4x^2)(3) + 3(2x)(9) + 27 = 8x^3 + 36x^2 + 54x + 27.