А)
18,28*1,2=21,936~22
18,28/1,2=15,2333..~15
б)
0,36*7,5=2,7~3
0,36/7,5=0,048~0,05
Ax+ay/x+y+xy=
=a(x+y)/x+y(1+x)=
a/(1+a)
1)t1=40/(22.5+2.5)=1.6ч
2)t2=48/(22.5-2.5)=2.4ч
3)v=(48+40)/(2.4+1.6)=22км/ч
y= - x²-x+9
y=f(x)
1) f(2)= - 2²-2+9=3;
f(2)=3
2) f(-3)= - (-3)²-(-3)+9= -9+3+9 = 3;
f(-3)=3
3) (k;3)
x=k;
y= 3;
3 = -k² -k +9;
k² + k - 6 =0
D=1-4·1·(-6) = 1+24 = 25 = 5²
k₁ = (-1-5)/2= -3
k₂ = (-1+5)/2= 2
k₁ = -3
k₂ = 2