1 + 1 - 1 + 5

= 2 - 1 + 5

= 1 + 5

= 6

Quá đơn giản

a)(2x-3)²=(x+5)²

=>4x²-12x+9=x²+10x+25

=>3x²-22x-16=0

=>3x²+2x-24x-16=0

=>x(3x+2)-8(3x+2)=0

=>(x-8)(3x+2)=0

=>x=8 hoặc x=-2/3

b)X².(x-1)-4x²+8x-4=0

=>x²(x-1)-4x²+4x+4x-4=0

=>x²(x-1)-4x(x-1)-4(x-1)=0

=>x²(x-1)-(4x-4)(x-1)=0

=>(x²-4x+4)(x-1)=0

=>(x-2)²(x-1)=0

=>x=2 hoặc x=1

c) 4x²- 25 - (2x- 5) . ( 2x+7)=0

=>4x²-25-(4x²+14x-10x-35)=0

=>4x²-25-4x²-14x+10x+35=0

=>-4x+10=0

=>-4x=-10 <=>x=5/2

d) x³+27+(x+3).(x-9)=0

=>x³+3³+(x+3)(x-9)=0

=>(x+3)(x²-3x+9)+(x+3)(x-9)=0

=>(x²-3x+9+x-9)(x+3)=0

=>(x²-2x)(x+3)=0

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

=>x=0 hoặc x=2 hoặc x=-3

e) (x-2).(x+5)- x²+4=0

=>(x-2)(x+5)-(x-2)(x+2)=0

=>(x-2)(x+5-x-2)=0

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