Question

bài 1: Rút gọn

a) (2x+3).(x+7) - (x+5).(1-x)

b) x.(x-2).(x+2) - (x² +1).(x²-1)

c) (x+2).(x² -2x+4) - (x-2).(x²+2x+4)

bài 2: Tìm x,biết

a) x² - 16- (x+4) = 0

b) (3x-1)² - (9x²-1)=0

c) 4x² + 9= -12x²

d) 4x² - 5x +1=0

e) 4x² - 4x +3=0

GIÚP MK VS, MAI MK PHẢI NỘP RỒI

Answer 1

Bài 2: 

a: \(x^2-16-\left(x+4\right)=0\)

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

=>(x+4)(x-5)=0

=>x=5 hoặc x=-4

b: \(\left(3x-1\right)^2-\left(9x^2-1\right)=0\)

\(\Leftrightarrow9x^2-6x+1-9x^2+1=0\)

=>-6x+2=0

=>-6x=-2

hay x=1/3

c: \(4x^2+9=-12x^2\)

\(\Leftrightarrow4x^2+12x^2=-9\)

\(\Leftrightarrow16x^2=-9\)(vô lý)

Do đó: \(x\in\varnothing\)

d: \(4x^2-5x+1=0\)

\(\Leftrightarrow4x^2-4x-x+1=0\)

\(\Leftrightarrow\left(x-1\right)\left(4x-1\right)=0\)

=>x=1 hoặc x=1/4

e: \(4x^2-4x+3=0\)

\(\Leftrightarrow4x^2-4x+1+2=0\)

\(\Leftrightarrow\left(2x-1\right)^2=-2\)(vô lý)

Do đó: \(x\in\varnothing\)