Which plane shape has 4 sides and is regular?

A quadrilateral is a plane figure formed by four sides. Common quadrilaterals are, square, rhombus, rectangle, parallelogram, kite (or deltoid) and a trapezium (or a trapezoid).

560

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answer:   x = 3 + √11     and     x = 3 - √11

step-by-step explanation:

x² - 6x + 9 = 11

(x - 3)² = 11

x - 3 = ±√11

    x = 3 ± √11

x = 3 + √11     and     x = 3 - √11