2 + 2=4 theo như moi người đã học
he researchers examined health records from about 20 million people for what they called the “world’s biggest obesity study.”
Obesity is a condition in which the body stores large, unhealthy amounts of fat. Obese individuals are considered overweight.
For the study, the researchers compared the body measurements of almost 20 million adults. They found that from 1975 to 2014, global obesity rates for men increased from 3.2 percent of the population to 10.8 percent. For women, it rose from 6.4 percent to 14.9 percent.
he researchers examined health records from about 20 million people for what they called the “world’s biggest obesity study.”
Obesity is a condition in which the body stores large, unhealthy amounts of fat. Obese individuals are considered overweight.
For the study, the researchers compared the body measurements of almost 20 million adults. They found that from 1975 to 2014, global obesity rates for men increased from 3.2 percent of the population to 10.8 percent. For women, it rose from 6.4 percent to 14.9 percent.
Объяснение:
Собственная скорость = х км/ч
Скорость по течению = х + 3 км/ч
Проплыл по течению = 30/(х + 3) км
Проплыл по озеру = 20/х км
30/(х + 3) + 20/х = 3
30 * х + 20*(х + 3) = 3 * х * (х + 3)
30х + 20х + 60 = 3х² + 9х
50х + 60 = 3х² + 9х
50х + 60 - 3х² - 9х= 0
-3х² + 41х + 60= 0 | * -1
3х² - 41х - 60 = 0
а = 3; в = -41; с = -60
Д = в² - 4ас
Д = (-41)² - 4 * 3 *(-60) = 1681 + 720 = 2401
√Д = √2401 = 49
х1 = (-в - √Д)/2а
х1 = (41 - 49)/2*3 = -8/6 = -4/3 = -1. 1/3
х2 = (-в + √Д)/2а
х2 = (41 + 49)/2*3 = 90/6 = 15
Так как скорость не может иметь отрицательное значение, берём за х положительный результат:
х = 15
Собственная скорость = (х) = 15 км/ч