@razin4419 -- You skipped certain key steps. You should put horizontal spaces and punctuation in for better readability. Don't use a period for multiplication. You should put parentheses around your fractions. I'll try a redo: Let a = x + 5 and b = x + 7, so we have b - a = 2. Now, we have : a⁴ + b⁴ = 272 and (b - a)⁴ = 16. From subtracting those equations, and dividing each side by 4, we find a³b + ab³ - (3/2)a²b² = 64. ab[a² + b² - 2ab + (1/2)ab] - 64 = 0 ab[(a - b)² + (1/2)ab] - 64 = 0 ab[(-2)² + (1/2)ab] - 64 = 0 because (a - b) = -2. ab[4 + (1/2)ab] - 64 = 0 2{ab[4 + (1/2)ab] - 64} = 2{0} to clear the fraction ab(8 + ab) - 128 = 0 8ab + (ab)² - 128 = 0 (ab)² + 8(ab) - 128 = 0 (ab + 16)(ab - 8) = 0 ab + 16 = 0 has no real solutions when combined with b - a = 2. ab - 8 = 0 ==> ab = 8 That, combined with b - a = 2, yields a = -4 and b = -2 ==> x = -9 *or* a = 2 and b = 4 ==> x = -3.

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