Question

a) x² - 16 - ( x - 4 ) = 0 
b) 6x ( x - 5 ) = x - 5      
c) x³ - 7x - 6 = 0
d) x³ - 4x² = -4x
e) (2x + 1)² = (3 + x)2
f) x² + y² - 6x + 6y +18 = 0
 

Answer 1

a: =>(x-4)(x+4)-(x-4)=0

=>(x-4)(x+3)=0

=>x=4 hoặc x=-3

b: \(\Leftrightarrow\left(x-5\right)\left(6x-1\right)=0\)

=>x=5 hoặc x=1/6

c: \(\Leftrightarrow x^3-x-6x-6=0\)

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

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

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

hay \(x\in\left\{3;-1;-2\right\}\)

e: \(\Leftrightarrow\left(2x+1-x-3\right)\left(2x+1+x+3\right)=0\)

=>(x-2)(3x+4)=0

=>x=-4/3 hoặc x=2