1 câu trả lời
` (n + 5)^2 = 64(n - 2)^3 `
` => (n + 5)^2 = 4^{3}(n - 2)^3 `
` => (n + 5)^2 = [4(n - 2)]^{3} `
` => (n + 5)^2 = (4n - 8)^{3} `
` => n^2 + 2n.5 + 5^2 = 4n^3 + 3.4n^{2}.8 + 3.4n.8^{2} - 8^{2} `
` => n^2 + 10n + 25 - 4n^3 + 96n^{2} + 768n - 64 = 0 `
` => -4n^{3} + n^{2} + 96n^{2} + 10n + 768n + 25 - 64 = 0 `
` => -4n^3 + 97n^2 + 778n - 39 = 0 `
` => n = 3 `
