Three sides of a quadrilateral measure 4.2 inches, 8 inches, and 5.8 inches. if the perimeter of the quadrilateral is 21.5 inches, what is the length of the fourth side

Can you me find the missing length. i attached an image.

Select the conic section that represents the equation. 3x2 + 3y2 -2x + 4 = 0

Urgent? will give brainliest given that the blue triangle is a right triangle, which expression correctly gives the area of the red square? a) a2 + b2 b) a2 - b2 c) a2 - c2 d) c2 - a2