Question

Tìm x, biết: 

a.  (3x - 5)(3x + 3) - (3x - 3)² = 9

b.  (x – 5)(x + 5) – (x + 6)² = 9

c.  (x – 2)(x + 5) + x(x + 5) = 0

d.  x² + 16x + 64 = 0

 

Giúp mình với ạ!!!! 

Answer 1

\(a,\Leftrightarrow9x^2-6x-15-9x^2+18x-9=9\\ \Leftrightarrow12x=33\Leftrightarrow x=\dfrac{33}{12}\\ b,\Leftrightarrow x^2-25-x^2-12x-36=9\\ \Leftrightarrow-12x=70\Leftrightarrow x=-\dfrac{35}{6}\\ c,\Leftrightarrow\left(2x-2\right)\left(x+5\right)=0\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-5\end{matrix}\right.\\ d,\Leftrightarrow\left(x+8\right)^2=0\Leftrightarrow x=-8\)

Answer 2

a)\(\dfrac{33}{12}\)

b)\(\dfrac{-35}{6}\)

c)x thuộc{1,-5}

d)-8