Question

B1tìm x bít

a,3x(2x-1)²-(2x-1).x=0

b,\(\dfrac{1}{2}\).(x+1)²-2.(x+1)=0

c, (2x+1)²-2x-1=0

B2a, CMR:50ⁿ⁺¹-50ⁿ \(⋮\)7

b, CMR: 45+4⁶+4⁷\(⋮\)²¹

^{lm giúp mk nhé mai mk phải nộp rùi}

Answer 1

Bài 1: 

a: \(3x\left(2x-1\right)^2-x\left(2x-1\right)=0\)

\(\Leftrightarrow x\left(2x-1\right)\left(6x-3-1\right)=0\)

=>x(2x-1)(6x-4)=0

hay \(x\in\left\{0;\dfrac{1}{2};\dfrac{2}{3}\right\}\)

b: \(\dfrac{1}{2}\left(x+1\right)^2-2\left(x+1\right)=0\)

\(\Leftrightarrow\left(x+1\right)\left(\dfrac{1}{2}x+\dfrac{1}{2}-2\right)=0\)

=>(x+1)(1/2x-3/2)=0

=>x=-1 hoặc x=3

c: \(\left(2x+1\right)^2-2x-1=0\)

=>(2x+1)(2x+1-1)=0

=>2x(2x+1)=0

hay \(x\in\left\{0;-\dfrac{1}{2}\right\}\)