Question

Expand: (p + 2q – r)2 using a suitable identity.

Answer 1

$(p+2q-r)^2=(p+2q-r)(p+2q-r)\\ \\perform\:the\: distribution\:of\:the\:first\:bracket\:over\:the\:second\:bracket. \\ \\(p+2q-r)^2=p(p+2q-r)+2q(p+2q-r)-r(p+2q-r) \\ \\ (p+2q-r)^2=p^2+2pq-pr+2pq+4q^2-2qr-pr-2qr+r^2 \\ \\(p+2q-r)^2=p^2+4pq-2pr-4qr+4q^2+r^2$