The intersection of a and b is the intersection of two straight lines of a and B.

When solving binary linear equations, X=0 and y=0.

So a crosses B={(x, y)|x=0, y=0}

From a to c

The two straight lines A and C are parallel and have no intersection.

So a goes through C= empty set.

(a to b) and (b to c)

The intersection of b and c is (3/5, -9/5).

So b crosses C={(x, y)|x=3/5, y=-9/5}

A cross B={(x, y)|x=0, y=0}

So (a crosses b) and (b crosses C)={(x, y) | (0,0), (3/5, -9/5)}

( 1)f(a)+ 1 =[ 1-a/ 1+a]+ 1 = 2/ 1+a

②f(a+ 1)=[ 1-(a+ 1)/ 1+(a+ 1)]+ 1 = 2/2+a

These are relatively simple problems. As long as you know the definition by heart and understand it, you can easily solve them. I think you will learn how to assemble. Come on! ! !