Question

tìm x

b, 3(x-2) = x(x-2) c, (x+3)^7 = 4(x+3).5 d, x-3.(x-3) = x-3

Answer 1

b) 3(x - 2) = x(x - 2)

3(x - 2) - x(x - 2) = 0

=> (x - 2)(3 - x) = 0

TH1 : x - 2 = 0

=> x = 2

TH2 : 3 - x = 0

=> x = 3

Vậy x = 2 hoặc 3

c) (x + 3)⁷ = 4(x + 3) . 5

=> (x + 3)⁷ = 20(x + 3)

=> (x + 3)⁷ - 20(x + 3) = 0

\(\Rightarrow\left(x+3\right)\left[\left(x+3\right)^6-20\right]=0\)

TH1 : x + 3 = 0

=> x = -3

TH2 : (x + 3)⁶ - 20 = 0

=> (x + 3)⁶ = 20 (loại)

Vậy x = -3

d) x - 3.(x - 3) = x - 3

=> x - 3x + 9 = x - 3

=> x - 3x - x = -3 - 9

=> -3x = -12

=> x = 4

Vậy x = 4