If someone could help me with 18 and 19 it would be much appreciated! :)

Terri makes a quilt using three sizes of fabric squares the side lenght of each fabric square is the square root of the area

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Use the following statements to write a compound statement for the conjunction or disjunction. then find its truth value. p: an isosceles triangle has two congruent sides. q: a right angle measures 90° r: four points are always coplanar. s: a decagon has 12 sides. a) a right angle measures 90° or an isosceles triangle has two congruent sides; true. b) a right angle measures 90° and an isosceles triangle has two congruent sides; true. c) a right angle measures 90° and an isosceles triangle does not have two congruent sides; false. d) a right angle measures 90° or an isosceles triangle does not have two congruent sides; true.