Question

Bai 2 : Tim x 

a/(3-x)^2-(5+x)^2=0

b/(x-3)^2-x(x+2)=7

c/x^2+8x-7=0

d/x^2+4x-5=0

 

Answer 1

Ta có : x² + 8x - 7 = 0

=> x² + 8x + 16 - 9 = 0

=> (x + 4)² - 9 = 0

=>  (x + 4)² = 9

=> \(\orbr{\begin{cases}x+4=3\\x+4=-3\end{cases}}\)

\(\Leftrightarrow\orbr{\begin{cases}x=-1\\x=-7\end{cases}}\)

Answer 2

a) (3-x)²-(5+x)²=0 => x=-1

b) (x-3)²-x(x+2)=7 => x=0,25

c) x²+8x-7=0   (ko biết làm)

d) x²+4x-5=0  => x=1

Answer 3

thank you 2 ban nhieu !!!