If $2 x+3 y+1=0$, then what is the value

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Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:

If $2 x+3 y+1=0$, then what is the value of $\left(8 x^3+8+27 y^3-18 x y\right)$ ?

Options:

-7

-9

Correct Answer:

Explanation:

We know that,

(a + b)³ = a³ + b³ + 3ab(a + b)

2x + 3y + 1 = 0

= 2x + 3y = -1

Now, (2x + 3y)³ = (2x)³ + (3y)³ + 3 × 2x × 3y (-1) = -1

= 8x³ + 27y³ – 18xy = -1

So, the value of (8x³ + 8 + 27y³ – 18xy)

= 8 – 1 = 7