57 + 58 + 59 + 60 + 61 + 62 + 63 + ...+140+141+142+143+144+... + 156 + 157 =
= (57+143)+ (58+142)+(59+141)+(60+140)+(61+139) + (62+ 138)+(63+137)+....(99+101)+100+144+145+146+147+148+149+150+151+152+153+154+155+156+157 = 200 * 43 + 100 + (144+156) + (145+155) + ...(149+151)+150 +157= 200 *43 + 6*300+ 100+150+157 = 8600 + 1800 + 407 = 10807
(6-13)*(32-41)=63
1) 6-13=-7
2) 32-41=-9
3) -7*(-9)=63
Надеюсь помогла!
665760 I 95
- 665 I-------
---------- 7008
7
- 0
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76
- 0
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760
-760
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=0=