A1+2d+a1+3d=2a1+5d=5/12
S6=(2a1+5d)*6/2=5/12*3=5/4
7sina+3sina=10sina
a=0,8 10sin0,8≈10*0,71=7,1
14-2,5x = 1,5x - 18
4x = 32, x = 8
y = 14 - 2,5.8 = 14 - 20 = -6
P=/8,-6/
32 - 4X = X^2
X^2 + 4X - 32 = 0
D = 16 + 128 = 144 ; V D = 12
X1 = ( - 4 + 12 ) : 2 = 4
X2 = ( - 16 ) : 2 = ( - 8 )