Question

Cho: \(-8.x=2\)và \(16y=-320\)

Tính:

A)\(x-y\)

b)\(4x-7y\)

Answer 1

Theo đề bài, ta có: 

\(-8x=2\Rightarrow x=\frac{2}{-8}=-\frac{1}{4}\)

\(16y=-320\Rightarrow y=-\frac{320}{16}=-20\)

\(\Rightarrow x:y=-\frac{1}{4}-\left(-20\right)=19,75\)

\(\Rightarrow4x-7y=\left(-\frac{1}{4}.4\right)-\left(7.\left(-20\right)\right)=-1-\left(-140\right)=139\)

Answer 2

\(-8x=2\Rightarrow x=-\frac{1}{4}\)

\(-16y=320\Rightarrow y=-20\)

a) Thay vào ta có

\(x-y=-\frac{1}{4}-\left(-20\right)=\frac{79}{4}\)

b) Thay vào ta có

\(4x-7y=4\left(-\frac{1}{4}\right)-7\left(-20\right)=-1-\left(-140\right)=139\)