Question

a) (2x + 1)^2 - 4(x + 2)^2 = 9;

b) (x + 3)^2 - (x - 4)( x + 8) = 1;
c) 3(x + 2)^2 + (2x - 1)^2 - 7(x + 3)(x - 3) = 36;

gấp trước 8h ngày mai
 

Answer 1

a: \(\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\)

=>-12x-15=9

=>x=-2

b: \(\Leftrightarrow x^2+6x+9-\left(x^2+8x-4x-32\right)=1\)

=>6x-8x+4x+9+32=1

=>2x+41=1

=>2x=-40

hay x=-20

c: \(\Leftrightarrow3x^2+12x+3+4x^2-4x+1-7x^2+63=36\)

=>8x+67=36

=>8x=-31

hay x=-31/8

Answer 2

Đây bạn nhé:

a) \((2x+1)^2-4(x+2)^2=9\)

\(\Leftrightarrow\) \((2x+1)^2-(2(x+2))^2=9\)

\(\Leftrightarrow\) \((2x+1-2x-4)(2x+1+2x+4)=9\)

\(\Leftrightarrow\) \(-3(4x+5)=9\)

\(\Leftrightarrow\) \(4x+5=-3\)

\(\Leftrightarrow\) \(4x=-8\)

\(\Leftrightarrow\) \(x=-2\)

b) \((x+3)^2-(x-4)(x+8)=1\)

\(\Leftrightarrow\) \(x^2+6x+9-(x^2+8x-4x-32)=1\)

 \(\Leftrightarrow\) \(x^2+6x+9-x^2-4x+32=1\)

\(\Leftrightarrow\) \(2x+40=0\) \(\Leftrightarrow\) \(x=-20\)

c) \(3(x+2)^2+(2x-1)^2-7(x+3)(x-3)=36\)

\(\Leftrightarrow\) \(3(x^2+4x+4)+4x^2-4x+1-7(x^2-9)=36\)

\(\Leftrightarrow\) \(7x^2+8x+13-7x^2+63=36\)

\(\Leftrightarrow\) \(8x+40=0\) \(\Leftrightarrow\) \(x=-5\)