Question

4/9x^2-25/16=0

Answer 1

`4/9x^2-25/16=0`

`4/9 x^2 = 0 + 25/16`

`4/9 x^2 = 25/16`

`x^2 = 25/16 : 4/9`

`x^2 = 25/16 xx 9/4`

`x^2 = 225/64`

`=>` \(x=\sqrt{\dfrac{225}{64}}\)

`=>` \(x=\left(\pm\dfrac{15}{8}\right)\)

Vậy `S = {15/8 ; -15/8}`

Answer 2

`4/9x^2-25/16=0`

`<=> 4/9 x^2 = 25/16`

`<=>x^2 = 25 /16 * 9/4 `

`<=> x^2 = 225/64`

`=>x = sqrt{225/64} = sqrt{(15/8)^2}`

`x = |15/8|`

`=> x = 15/8 (hoặc) x = -15/8`

Vậy `x∈{15/8 ; -15/8}`