21×5.79+62×5.79+17×5.79
=5.79×（21+62+17）
=5.79×100
=579;
1.222²×9-1.333²×4
=(1.222×3+1.333×2)(1.222×3-1.333×2)
=(3.666+2.666)×(3.666-2.666)
=6.332
如果本题有什么不明白可以追问,