Question

Giải phương trình:

a,\(\sqrt{x-5}=3\)

b,\(\sqrt{4-5x}=12\)

c,\(\sqrt{x^2-6x+9}=3\)

d,\(\sqrt{4x+20}+\sqrt{x+5}-\dfrac{1}{3}\sqrt{9x+45}=4\)

Answer 1

a, \(\sqrt{x-5} = 3 \)

<=> x - 5 = 9

<=> x = 14.

b, \(\sqrt{4-5x}=12\)

<=> 4 - 5x = 144

<=> 5x = -140

<=> x = -28.

c, \(\sqrt{x^{2}-6x+9}=3\)

<=> x² - 6x + 9 = 9

<=> (x - 3)² = 9

TH1:

x - 3 = 3

<=> x = 6.

TH2:

x - 3 = -3

<=> x = 0

d, \(\sqrt{4x+20}+\sqrt{x+5}-\dfrac{1}{3} \sqrt{9x+45}=4\)

<=> \(2\sqrt{x+5}+\sqrt{x+5}-\sqrt{x+5} = 4\)

<=> \(2\sqrt{x+5}\)= 4

<=> \(\sqrt{x+5}\) = 2

<=> x + 5 = 4

<=> x = -1.

Answer 2

\(\sqrt{x-5}=3\Leftrightarrow x-5=9\Leftrightarrow x=14\)

Answer 3

\(\sqrt{4-5x}=12\Leftrightarrow4x-5=144\Leftrightarrow4x=149\Leftrightarrow x=37,25\)