#zad1
A=[2,-2,1,-1;-1,4,-5,3;1,1,-1,1;-4,2,1,-2];
b=[7;1;4;6];
A\b
#zad2
syms x
solve(x^3-21*x+20==0,x)
#zad3
x=-2.0:0.05:2;
y=-2.0:0.05:2;
plot(x,x.^2-2*x+3);
plot(x,cos(2*x),"+k");
plot(x,sin(1./x),"*b");
grid on
x=-2:0.1:2;
y=-2:0.1:2;
[xx,yy]=meshgrid(x,y);
mesh(xx, yy, xx.^2+yy.^2)
mesh(xx, yy, xx.^2-yy.^2 + 2*x.*y.^2+1)