Question

solve it in a proper and easily understandable way

Answer 1

14³+16³+18³+20³+...+30³

=2³{7³+8³+9³+10³+...+15³}

=8{(1³+2³+3³......15³)-(1³+2³+3³+......+6³)}

=8{[15(16)/2]²-[6(7)/2]²}

=8{[15×8]²-[21]²}

=8×9{[40²]-7²}

=8×9×1551【3,102→6,204→12,408】

=9×12,408

=124,080–12,408

=112,000+80–408【-328】

=111,672