Question

bài 1: tìm x không âm biết

a) \(\sqrt{x}=5\) b) \(\sqrt{x+1}=2\)

c) \(\sqrt{x^2}=4\) d) 2\(\sqrt{x+1}=4\)

bài 2: tính

a) \(\sqrt{\left(-15\right)^2}\) b) \(\sqrt{\left(2-\sqrt{5}\right)^2}\) c) \(\sqrt{\left(3-\sqrt{7}\right)^2}\)

d) 2\(\sqrt{a^2}\) với a<_ 0 e) \(\sqrt{a-2}\) ( a<2)

Answer 1

2) \(a.\sqrt{\left(-15\right)^2}=\left|15\right|=15\)

\(b.\sqrt{\left(2-\sqrt{5}\right)^2}=\left|2-\sqrt{5}\right|=2-\sqrt{5}\)

\(c.\sqrt{\left(3-\sqrt{7}\right)^2}=\left|3-\sqrt{7}\right|=3-\sqrt{7}\)

\(d.2\sqrt{a^2}=\left|2\sqrt{a}\right|=2\sqrt{a}\)

Answer 2

bai1

a)

√x=5=> x=25

b)

√(x+1)=2; x+1=4;x=3

c)

√(x^2)=4=> x=±4; x>0=>x=4

d)

2√(x+1)=4=>√(x+1)=2

x+1=4;x=3

Answer 3

bai 2.

a)√(-15)^2=15

b)√[2-√5]^2=|2-√5|=√5-2

c)√(3-√7)^2=|3-√7|=3-√7

d)2√(a^2)=2|a|=-2a

e)

√(a-2); a<2; => ko ¥

Answer 4

câu b,c,d ghi nhầm

\(\sqrt{5}-2\)

\(\sqrt{7}-3\)

\(2\sqrt{a^2}=\sqrt{2^2.a^2}=\sqrt{\left(2.a\right)^2}=\left|2a\right|=2a\)