2у + 4х = 94
х - 2у = 0
2у + 4х = 94
+
-2у + х = 0
____
5х = 94
х = 18,8
х = 18,8
18,8 - 2у = 0
х = 18,8
у = 9,4
ОТВЕТ: (18,8 ; 9,4)
2x^3-1/3y^2=2*(1/2)^3-1/3*(-3)^2=2*0.5^3-(-3)^2/3=0.25-(-3)^2/3=0.25-9/3=0.25-3=-2.75
Xn=X1+d(n-1)
X2=X1+d(2-1)
70=X1+d
-X1=d-70
X1=-d+70
X4=X1+d(4-1)
-10=(-d+70)+3d
-10=2d+70
-80=2d
d=-40
X1=40+70=110
S_{10}=10*\frac{2*110-40(10-1)}{2}=-700
Ответ: -700.
5х^2+х=4
5х^2+х-4=0
D=1+80=81=9^2
x1= -1+9/10=8/10=4/5
x2=-1-9/10= -10/10= -1