Question

如果3Y等于X加上2Z,那么X的平方加上9Y的平方加上4Z的平方减去6XY减去12YZ加上4XZ

Answer 1

x^2+9y^2+4z^2-6xy-12yt-4xz

=x^2+(x+2z)^2+4z^2-2x(x+2z)-4z(x+2z)+4xz

=x^2+x^2+4xz+4z^2+4z^2-2x^2-4xz-4xz-8z^2+4xz

=0