Let a and b be the solutions to 5x^2 - 11x + 4 = 4x^2 - 17x + 6. Find 1/a^3 + 1/b^3.
Simplifying the equation, we have \(x^2 + 6x - 2 = 0 \)
In the form mx^2 + nx + p = 0, the Product of the roots ab = -n/m = -2
So 2ab = -4
Sum of the roots a + b = p/m = -6
Squaring both sides, we have
\(a^2 + b^2 + 2ab = 36 \\ a^2 + b^2 - 4 =36 \\ a^2 + b^2 = 40 \)
\(1/a^3 + 1/b^3 = \\(a^3 + b^3) / (ab)^3 \) Note : a^3 + b^3 = (a + b) (a^2 + b^2 - ab)
So we have
\((a + b) ( a^2 + b^2 -ab) / (ab)^3 = \\ (-6) (40 - -2) / (-8) = \\ (6) (42 / 8) = 31.5 \)
Thus, the answer is 31.5
Thanks! :)