Cut a triangle from a trapezoid with an upper bottom of 5 cm and a lower bottom of 8 cm and a height of 6 cm. The maximum area of the triangle is () square cm A15 b；19.5 c；24

Cut a triangle from a trapezoid with an upper bottom of 5 cm and a lower bottom of 8 cm and a height of 6 cm. The maximum area of the triangle is () square cm A15 b；19.5 c；24

Select C6 × 8 △ 2 = 24 square centimeter

Two triangles of equal area, one is 12 cm high, the bottom is twice as high, and the other is 12 cm high
30 cm. What's the height of the bottom?

12*24/30=9.6

The area of the rectangle is 10. If the length of the rectangle is x, the width is x, the diagonal is D, and the perimeter is l, what functions can you get about these quantities?
I know the answer, but I see this one in the answer book. I don't understand it
L = 2 * radical d ^ 2 + 20
What's the matter with this one?
What did 20 come from. Width is y, wrong number on it

D & sup2; is the square sum of length and width, and 10 (area) is the product of length and width. The sum of the two can form the square of the sum of length and width
(d ^ 2 + 20) he adds a root to the sum of length and width, and multiplies 2 to the circumference
D & sup2; = x & sup2; + Y & sup2;, 10 = XY D square + 20 = (x + y) square
(ask if it's wide or y)