Đáp án:
a, `69^2 + 31^2 + 69 . 63`
` = (69 + 31)^2`
` = 100^2 = 10000`
b, `158^2 + 42^2 + 85 . 158`
` = (158 + 42)^2 + 158`
` = 200^2 + 158`
` = 20000 + 158`
` = 20 158`
c, `312 . (312 -24) + 144`
` = 312^2 - 312 . 24 + 12^2`
` = (312 - 12)^2`
` = 300^2 = 90000`
d, `0,57^2 + 0,43^2 + 99 . 101 + 0,86 . 0,57`
` = (0,57 + 0,43)^2 + 100^2 - 1^2`
` = 1^2 + 100^2 - 1^2`
` = 100^2 = 10000`