(6 3/5 ÷ <span>6 - 8,016 </span>× <span>0,125 + 5/12 </span>× 0,03) × <span>2 3/4 = 2431/8000
1) 6 3/5 </span>÷ 6 = 33/5÷6 = 6,6÷6=1,1<span>
2)8,016 </span>× 0,125 = 1,002<span>
3)5/12 </span>× 0,03 = 5/12 × 3/100 = 1/80<span>
4)1,1-1,002=0,098
5)0,098 + 1/80 = 98/1000 + 1/80 = 49/500 + 1/80 = (49 × 4 + 1 × 25)/2000 = 196/2000 + 25/2000 = 221/2000
6)221/2000 </span>× 2 3/4 = 221/2000 ×11/4 = 2431/8000
"Перевернём" всё:
x=1/(1/y+1/z)=1/((z+y)/zy)=zy/(z+y)
4х(х+3)-(2х+5)(2х-5)=49
4х²+12х-((2х)²-5²)=49
4х²+12х-4х²+25=49
12х=49-25
12х=24
Х=2
Пусть числа n, (n+1), (n+2), (n+3).
(n+1)(n+3)-(n+2)*n=31,
n^2+n+3n+3-n^2-2n=31,
2n=31-3,
2n=28,
n=14,
ответ: 14; 15; 16; 17.
15*17-14*16=255-224=31.