Question

Giải giúp a b

Answer 1

a) ĐK: x ≤ 2

PT <=> 2 - x = 9

,=> x = -7

b) PT <=> \(\sqrt{\left(2-x\right)^2}=3\)

<=> 2 - x = 3

<=> x = -1

c) PT <=> \(\sqrt{4+x^2}=3-x\)

\(\Leftrightarrow4+x^2=9-6x+x^2\)

\(\Leftrightarrow-6x+5=0\)

\(\Leftrightarrow x=\dfrac{5}{6}\)

d) PT <=> \(\dfrac{1}{2}\sqrt{16\left(x-2\right)}-2\sqrt{4\left(x-2\right)}+\sqrt{9\left(x-2\right)}=5\)

\(\Leftrightarrow\dfrac{1}{2}.4.\sqrt{x-2}-2.2.\sqrt{x-2}+3.\sqrt{x-2}=5\)

\(\Leftrightarrow\sqrt{x-2}\left(\dfrac{1}{2}.4-2.2+3\right)=5\)

\(\Leftrightarrow\sqrt{x-2}=5\)

\(\Leftrightarrow x-2=25\)

<=> x = 27

 

Answer 2

   a) \(\sqrt[]{2-x}\) = 3

⇔ 2 - x = 9

⇔ x      = -7

vậy....

 b)\(\sqrt{4-4x+x^2}\) =3

⇔ \(\sqrt{\left(2-x\right)^2}\) =3

⇔ I2 - xI=3

⇔ x - 2 = 3 (vì x>2)

⇔ x = 5

vậy.....