Question

Tìm x thuộc Z, biết:

a) 3.(x+2)_6.(x-5)=2.(5-2x)

b) (-2x).(-4x)+28=100

Answer 1

a, 3(x+2)-6(x-5)=2(5-2x)

    3x+6-6x+30=10-4x

    3x+6-6x+30-10+4x=0

    3x-6x+4x+6+30-10=0

    x+26=0

    x= -26

b, (-2x)(-4x)+28=100

     8x² + 28=100

     8x² = 72

       x²  = 9

     => x=3 hoặc x= -3

Answer 2

a/ 3(x+2) - 6(x-5) = 2(5-2x)

<-> 3x+6-6x+30 = 10-4x

<-> x = -26

b/  (-2x)(-4x) + 28 = 100

<-> 8x = 72

<-> x =  9