Question

tms x biết

a,\(\sqrt{2x+3}=3-\sqrt{5}\)

b,\(\sqrt{5+\sqrt{7x}}=2+\sqrt{7}\)

c,(\(\sqrt{x}-2\))\(\left(5-\sqrt{x}\right)=4-x\)

m.n nhanh giúp e với

Answer 1

a, \(\sqrt{2x+3}\)= 3-\(\sqrt{5}\)

⇔ 2x+3=(3-\(\sqrt{5}\))² ⇔2x = 3²-2.3.\(\sqrt{5}\) +5-3 = 11-6\(\sqrt{5}\)

⇔ x = \(\dfrac{11-6\sqrt{5}}{2}\)

Answer 2

b: \(\Leftrightarrow5+\sqrt{7x}=11+4\sqrt{7}\)

=>\(\sqrt{7x}=6+4\sqrt{7}\)

=>\(7x=\left(4\sqrt{7}+6\right)^2\)

hay \(x=\dfrac{\left(4\sqrt{7}+6\right)^2}{7}\)

c: \(\Leftrightarrow5\sqrt{x}-x-10+2\sqrt{x}=4-x\)

=>7 căn x=14

=>căn x=2

=>x=4