Question

Bao Yu is completing the square to solve the polynomial equation.

x2 – x – 3 = 0

What should be her first step?

adding –x to both sides of the equation
adding –3 to both sides of the equation
isolating the first term, x2
isolating the constant, –3

Answer 1

Answer:

isolating the constant,-3

Answer 2

$\\ \sf\longmapsto {x}^{2} - x - 3 = 0 \\ \\ \sf\longmapsto {x}^{2} - x = 3 \\ \\ \sf\longmapsto 4( {x}^{2} - x) = 4 \times 3 \\ \\ \sf\longmapsto 4 {x}^{2} - 4x = 12 \\ \\ \sf\longmapsto {(2x)}^{2} - 2 \times 2x \times 1 = 12 \\ \\ \sf\longmapsto {(2x)}^{2} - 2 \times 2x \times 1 + {1}^{2} = 12 + 1 {}^{2} \\ \\ \sf\longmapsto {(2x - 1)}^{2} = 12 + 1 \\ \\ \sf\longmapsto {(2x - 1)}^{2} = 13 \\ \\ \sf\longmapsto 2x - 1 = \pm \sqrt{13} \\ \\ \sf\longmapsto 2x = 1 \pm \sqrt{13} \\ \\ \sf\longmapsto x = \frac{1 \pm \sqrt{13} }{2}$