Question

if a-b= 7 and a² - b² = 85
find a3-b3​

Answer 1

HEY HERE IS UR ANSWER---

$a - b = 7$

${a}^{2} = 7 + b$

${a}^{2} + {b}^{2} = 85$

$(7 + b) {}^{2} + {b = 85 } \\ 49 + {b + 14b + { b}^{2} } = 85 \\ 2b {}^{2} + 14b - 36 = 0 \\ {b + 7b}^{} - 18 = 0 \\ b + 9b - 2b -18 = 0 \\ b(b + 9) - 2(b + 9) = 0 \\ b = 2 \\ \\ a - b = 7 \\ a = 9 \\ {a}^{3} - {b}^{3} \\ 729 - 8 = 721$

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