Question

If a - b = 4 nd ab =21, find the value of a^3 -b^3 *​

Answer 1

Answer:

${a}^{3} - {b}^{3} = (a - b)( {a}^{2} + {b}^{2} + ab)$

${a}^{3} - {b}^{3} = (4)( {a}^{2} + {b}^{2} + 21)$

${a}^{3} - {b}^{3} = 4 {a}^{2} + 4 {b}^{2} + 84$

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Answer 2

Answer:

• 316

Step-by-step explanation:

$a {}^{3} - b {}^{3} \\ = (a - b) {}^{3} + 3ab(a - b) \\ = (4 {}^{3}) + 3 \times 21 \times (4) \\ = 316$