Answer:
1. 50 m
2. 80 cm
Step-by-step explanation:
1. There are 2 triangles, subtract the area of 1 of them from the other.
The triangle that needs to be subtracted: b = 20 m, h = 10 m
A = 1/2b * h = 1/2(20) * 10 = 10*10 = 100 m
The big triangle, the one that needs to be subtracted plus the one you need to find the area of: b = 20 cm, h = 15 cm, 1/2(20) * 15 = 10 * 15 = 150
150 - 100 = 50 c
2. Divide it into 3 parts:
1- 3*4 = 12
2. 7*(4 + 4) = 7*8 = 56
3. [(4 + 4) * (13 - 7 - 3)]/2 = (8*3)/2 = 24/2 = 12
12 + 56 + 12 = 80 cm
B is the correct answer R=Q-7s/4
Area of ABC : AB*AC/2
the maximum of the parabola is reached at x=-4/(2*(-1))=2 hence A is at (2,0) and B is at (2,(-2)^2+4*2+C)=(2,12+C)
C is the second root (x-intersect), which we can find :
determinant1 : D=16-4*(-1)*C=4(4+C) thus the second root is at x=

Hence the area of the triangle is

hence

.
We remark that

Hence 4+C=16 thus
C=12
A and D are the correct answers