If $(2 a + b) = 12$ and $a b = 15$ , then find the value of $8 a^{3} + b^{3}$ .

646

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648

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654

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656

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Solution

The correct option is B $648$
$(2 a)^{3} + b^{3} = (2 a + b) [(2 a)^{2} + b^{2} - 2 a b]$
$= (2 a + b) [(2 a + b)^{2} - 6 a b] = 12 \times 54 = 648$

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Similar questions

a - b = 2

ab = 15

a^{3} - b^{3}

8 a^{3} - b^{3} - 4 a x + 2 b x

a + b + c = 0

(a + b - c)^{3} + (b + c - a)^{3} + (c + a - b)^{3}

If $a + b + c = 0$ , then the value of $(a + b - c)^{3} + (b + c - a)^{3} + (c + a - b)^{3}$ is:

8 a^{3} + b^{3} + 12 a^{2} b + 6 a b^{2}

= (2 a + b) (2 a + b) (2 a + b)

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