Question

(√21-√18)*(√21-√18) помогите пожалуйста

Answer 1

$(sqrt{21}-sqrt{18})(sqrt{21}-sqrt{18})=(sqrt{21}-sqrt{18})^2=(sqrt{21})^2-2cdotsqrt{21}cdotsqrt{18}+\ \ +(sqrt{18})^2=21-2sqrt{378}+18=39-2sqrt{378}$