Pearl solved a system of equations using substitution. Did she do it correctly? How do you know? If she did not find her error and solve the system correctly. 2x + (-5 - x) = 20 r-5= 20 X-5 + 5 = 20 + 5 x= 25 System: y=-5-X 2x + y = 20 Pearl's Solution: r = 25 y = -30

Here is their argument. given the obtuse angle x, we make a quadrilateral abcd with ∠dab = x, and ∠abc = 90◦, and ad = bc. say the perpendicular bisector to dc meets the perpendicular bisector to ab at p. then pa = pb and pc = pd. so the triangles pad and pbc have equal sides and are congruent. thus ∠pad = ∠pbc. but pab is isosceles, hence ∠pab = ∠pba. subtracting, gives x = ∠pad−∠pab = ∠pbc −∠pba = 90◦. this is a preposterous conclusion – just where is the mistake in the "proof" and why does the argument break down there?

Find the total area for the regular pyramid ( follow the answer set up in the picture)

Factor the expression using gcf 9b+45