Question

giải phương trình:

a, \(\sqrt{25x+75}+3\sqrt{x-2}=2+4\sqrt{x+3}+\sqrt{9x-18}\)

b, 4^x-10.2^x+16=0

c, x(x-1)(x+4)(x+5)=84

Answer 1

a: \(\Leftrightarrow5\sqrt{x+3}-4\sqrt{x+3}=3\sqrt{x-2}-3\sqrt{x-2}+2\)

\(\Leftrightarrow\sqrt{x+3}=2\)

=>x+3=4

hay x=1

c: \(\Leftrightarrow\left(x^2+4x\right)\left(x^2+4x-5\right)=84\)

\(\Leftrightarrow\left(x^2+4x\right)^2-5\left(x^2+4x\right)-84=0\)

\(\Leftrightarrow\left(x^2+4x\right)^2-12\left(x^2+4x\right)+7\left(x^2+4x\right)-84=0\)

\(\Leftrightarrow x^2+4x-12=0\)

=>(x+6)(x-2)=0

=>x=-6 hoặc x=2