03-16-2019, 04:50 PM

Recently purchased Casio FX-115ES Plus (used). Discovered a minor Quadratic Solver bug.

Example: solve G(y) = 11713 y^2 + 5346 y + 610 = 0

Casio FX-115MS Quad Solver => y = -0.228207974 ± 8.537522411e-5 * I

Casio FX-115ES Quad Solver => y = −0.228207974 ± 8.537522474e-5 * I

What seems to happen is FX-115ES solving: y^2 + 5346/11713 * y + 610/11713 = 0

Luckily, we can by-pass the bug, by scaling z = 11713 y

→ solve z^2 + 5346 * z + 610*11713 = 0

→ z = -2673 ± I

→ y = (-2673 ± I)/11713 = Casio FX-115MS result

Update: unfortunately, cubic solver bug still there.

Tried solving x^3 + 3000 x^2 + 3000170 x + 16000 = 0

Small root = -0.053330 59568, but solver gives +0.051330 69857 ???

Example: solve G(y) = 11713 y^2 + 5346 y + 610 = 0

Casio FX-115MS Quad Solver => y = -0.228207974 ± 8.537522411e-5 * I

Casio FX-115ES Quad Solver => y = −0.228207974 ± 8.537522474e-5 * I

What seems to happen is FX-115ES solving: y^2 + 5346/11713 * y + 610/11713 = 0

Luckily, we can by-pass the bug, by scaling z = 11713 y

→ solve z^2 + 5346 * z + 610*11713 = 0

→ z = -2673 ± I

→ y = (-2673 ± I)/11713 = Casio FX-115MS result

Update: unfortunately, cubic solver bug still there.

Tried solving x^3 + 3000 x^2 + 3000170 x + 16000 = 0

Small root = -0.053330 59568, but solver gives +0.051330 69857 ???