Question

Tìm x :

a ) ( 9 - 8x ) 2 = 100

b ) ( 20 - x ) 2 = 60

c ) \(\frac{1}{2}x+\frac{8}{4}=\frac{100}{25}\)

d ) ( 90 - x ) 10 = 1000

Answer 1

a, (9-8x)x2=100

     9-8x    =100:2

     9-8x   =50

        8x    =9-50

        8x    =-41

        x     =-41:8

        x     = \(\frac{-41}{8}\)

b, (20-x)x2=60

     20-x    =60:2

     20-x    =30

         x    =20-30

        x    =-10

c, \(\frac{1}{2}x+\frac{8}{4}=\frac{100}{25}\)

   \(\frac{1}{2}x+2=4\)

  \(\frac{1}{2}x=4-2\)

   \(\frac{1}{2}x=2\)

      x   =2:\(\frac{1}{2}\)

     x    =4

d, (90-x)10=1000

    90-x     =1000:10

    90-x     =100

        x      =90-100

        x=-10

****

Answer 2

d)(90-x)10=1000

<=>90-x=1000:10

<=>90-x=100

<=>x=90-100

<=>x=-10