quadratic equation

(algebra 代数) equation that uses the square (and no higher power) of an unknown quantity, eg x^2 + 2x - 8 = 0 二次方程式（如 x^2 + 2x - 8 = 0）.

QB, QC, QE2, QED, qr, qt, qto, qty, qua, quack, quack-quack, quackery, quad, quadr(i)-, Quadragesima, quadrangle, quadrangular, quadrant, quadraphonic (also quadrophonic), quadraphony (also quadrophony), quadrennial, quadrilateral, quadrille, quadrillion, quadrophonic, quadrophony, quadruped, quadruple, quadruplet, quadruplicate, quaff, quagmire, quail, quaint, quaintly, quaintness, quake, Quaker, qualification, qualified, qualifier,