Question

giúp tớ,tớ cần gấp

Answer 1

a, \(\dfrac{x}{4}=\dfrac{y}{7};xy=112\)
Ta có: \(\dfrac{x}{4}=\dfrac{y}{7}=\dfrac{x.y}{4.7}=\dfrac{112}{28}=4\)
*\(\dfrac{x}{4}=4=>x=16\)
*\(\dfrac{y}{7}=4=>y=28\)
Vậy (x, y)\(\in\){ 16, 28}
Nhiều quá, nên tách ra nha

Answer 2

c, \(4x=5y;xy=80\)
= \(\dfrac{4x}{1}=\dfrac{5y}{1}=\dfrac{x}{\dfrac{1}{4}}=\dfrac{y}{\dfrac{1}{5}}=\dfrac{xy}{\dfrac{1}{4}.\dfrac{1}{5}}=\dfrac{80}{\dfrac{1}{20}}=1600\)
=> \(4x=1600=>x=400\)
     \(5y=1600=>y=320\)
Vậy( x; y)∈{ 400; 320

Answer 3

e, \(\dfrac{x}{-9}=\dfrac{y}{4};xy=-36\)
Ta có: \(\dfrac{x}{-9}=\dfrac{y}{4}=\dfrac{xy}{\left(-9\right).4}=\dfrac{-36}{-36}=1\)
* \(\dfrac{x}{-9}=1=>x=-9\)
* \(\dfrac{y}{4}=1=>y=4\)
Vậy( x, y) ∈{ -9; 4}

Answer 4

e, \(\dfrac{a}{2}=\dfrac{b}{3}=\dfrac{c}{4};abc=648\)
Ta có: \(\dfrac{a}{2}=\dfrac{b}{3}=\dfrac{c}{4}=\dfrac{abc}{2.3.4}=\dfrac{648}{24}=27\)
*\(\dfrac{a}{2}=27=>a=54\)
* \(\dfrac{b}{3}=27=>b=81\)
* \(\dfrac{c}{4}=27=>c=108\)
Vậy( a, b, c)∈{ 54, 81, 108}