If a + 2b = 5, then find the value of $a^{3} + 8 b^{3} + 30 a b$ .

100

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125

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150

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Solution

The correct option is B 125
Given a + 2b = 5;
$(a + 2 b)^{3} = a^{3} + (2 b)^{3} + 3 \times a \times 2 b \times (a + 2 b)$

$5^{3} = a^{3} + 8 b^{3} + 6 a b \times 5$ .... ( since a + 2b = 5)

$∴$ $a^{3} + 8 b^{3} + 30 a b$ = 125

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Similar questions

a + 2 b = 5

a^{3} + 8 b^{3} + 30 a b = 125

a^{3} - 8 b^{3} - 36 a b - 216

a = 2 b + 6

a^{3} + 8 b^{3} + c^{3}

a^{3} + 8 b^{3} + c^{3} = 6 a b c

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

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