Question

bài 1

a,(x+7) :x=4:5

b,(x-20):(x+40)=(x+70):(x-10)

Answer 1

a)\(\frac{x+7}{x}=\frac{4}{5}\)

=>5(x+7)=4x

5x+35=4x

5x-4x=-35

x=-35

Vậy x=-35

b)(x-20)/(x+40)=(x+70)/(x-10)

(x-20)*(x-10)=(x+40)*(x+70)

x(x-10)-20(x-10)=x(x+70)+40(x+70)

x²-10x-20x+200=x²+70x+40x+2800

x²-x²-10x-20x-70x-40x=2800-200

0-(10x+20x+70x+40x)=2600

-140x=2600

x=2600/(-140)

x=\(-\frac{130}{7}\)

Vậy x=-130/7