Expand (2a−3b)5 by binomial theorem
Let A={a1,a2,a3,a4,a5} and B={b1,b2,b3,b4,b5} where ai's and bi's are school going students . Define a relation from A to B by xRy iff y is a true friend of x . If R={(a1,b1),(a2,b2),(a3,b3),(a4,b4),(a5,b5)} . Prove that R is neither one one nor onto