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7 September, 10:14

Solve each system by elimination.

y=2x^2+x-1

x-2y=6

+3
Answers (1)
  1. 7 September, 10:25
    0
    Y = 2x² + x - 1

    x - 2y = 6

    x - 2 (2x² + x - 1) = 6

    x - 4x² - 2x + 2 = 6

    x - 2x - 4x² + 2 = 6

    -x - 4x² + 2 = 6

    -x - 4x² - 4 = 0

    -4x² - x - 4 = 0

    x = - (-1) + / - √ ((-1) ² - 4 (-1) (-4))

    2 (-4)

    x = 1 + / - √ (1 - 16)

    -8

    x = 1 + / - √ (-15)

    -8

    x = 1 + / - i√ (15)

    -8

    x = 1 + i√ (15) x = 1 - i√ (15)

    -8 - 8

    x = - 0.125 - i√ (15) x = - 0.125 + i√ (15)

    y = 2x² + x - 1

    y = 2 (-0.125 - i√ (15)) ² + (-0.125 - i√ (15)) - 1

    y = 2 (0.015625 + 2i√ (15) + 15) - 0.125 - i√ (15) - 1

    y = 0.03125 + 4i√ (15) + 30 - 0.125 - i√ (15) - 1

    y = 0.03125 + 30 - 0.125 - 1 + 4i√ (15) - i√ (15)

    y = 29.1875 + 3i√ (15)

    (x, y) = (-0.125 - i√ (15), 29.1875 + 3i√ (15))

    or

    y = 2x² + x - 1

    y = 2 (-0.125 + i√ (15)) + (-0.125 + i√ (15) - 1

    y = 2 (0.015625 - 2i√ (15) - 15) - 0.125 + i√ (15) - 1

    y = 0.3125 - 4i√ (15) - 30 - 0.125 + i√ (15) - 1

    y = 0.3125 - 30 - 0.125 - 1 - 4i√ (15) + i√ (15)

    y = - 30.8125 - 3i√ (15)

    (x, y) = (-0.125 + i√ (15), - 30.8125 - 3i√ (15))
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