?

d,<=>\(\dfrac{x-90}{10}+\dfrac{x-76}{12}+\dfrac{x-58}{14}+\dfrac{x-36}{16}-10=0\)

<=>\(\dfrac{x-90-10}{10}+\dfrac{x-76-24}{12}+\dfrac{x-58-42}{14}+\dfrac{x-36-64}{16}=0\)

<=>(x-100)(\(\dfrac{1}{10}+\dfrac{1}{16}+\dfrac{1}{14}+\dfrac{1}{12}\))=0

<=>x=100

Vậy....

a,5x-20=0

<=>5x=20

<=>x=4

Vậy ....

b,<=>(x+5)(x-\(\dfrac{1}{2}\))=0

<=> x=-5 hoặc x=\(\dfrac{1}{2}\)

Vậy ....