x - 2/5 = -3/10

( x - 1/2 ) : 5/11 = 11/4

1/2 . x² - 4½ = 0

Giúp e vs ạ

` a) x-2/5=(-3)/10 `

` => x=(-3)/10+2/5 `

` => x=(-3)/10+4/10 `

` => x=1/10 `

` b) (x-1/2) : 5/11 = 11/4 `

` => x-1/2 = 11/4 . 5/11 `

` => x-1/2=5/4 `

` => x=5/4+1/2 `

` => x=5/4+2/4 `

` => x=7/4 `

` c) 1/2 . x^2 - 4 1/2 = 0 `

` => 1/2 . x^2 - 9/2 = 0 `

` => 1/2 . x^2 = 9/2 `

` => x^2 = 9/2 : 1/2 `

` => x^2 = 9/2 . 2 `

` => x^2 = 9 `

` => x={±3} `