Question

[Phạm Minh Hiền]

Bài 1:Tính
1.\(\sqrt{12,5}\cdot\sqrt{0,2}\cdot\sqrt{0,1}\)
2.\(\sqrt{48,4}\cdot\sqrt{5}\cdot\sqrt{0,5}\)
Bài 2:Khai triển các hằng đẳng thức sau:
a,\(\left(\sqrt{7}+\sqrt{3}\right)^2\)
b,\(\left(\sqrt{11}-\sqrt{5}\right)^2\)
c,\(\left(\sqrt{x}+\sqrt{y}\right)^2\)
d,\(\left(\sqrt{13}+\sqrt{7}\right)^2\)
e,\(\left(\sqrt{a}-\sqrt{b}\right)^2\)
f,\(\left(\sqrt{3}-1\right)^2\)

Answer 1

[Silverbullet]

B1:

1. \(\sqrt{12.5}\cdot\sqrt{0.2}\cdot\sqrt{0.1}\) \(=\sqrt{12.5\cdot0.2\cdot0.1}\) \(=\sqrt{0.25}=0.5\)

2.\(\sqrt{48.4}\cdot\sqrt{5}\cdot\sqrt{0.5}\) = \(\sqrt{48.4\cdot5\cdot0.5}\) =\(\sqrt{121}=11\)

B2:

a, \(\left(\sqrt{7}+\sqrt{3}\right)^2=7+2\cdot\sqrt{7}\cdot\sqrt{3}+3=7+2\cdot\sqrt{21}+3\)\(=10+2\sqrt{21}\)

b,\(\left(\sqrt{11}-\sqrt{5}\right)^2=11-2\sqrt{55}+5=16-2\sqrt{55}\)

c,\(\left(\sqrt{x}+\sqrt{y}\right) ^2=x+2\sqrt{xy}+y\)

d.\(\left(\sqrt{13}+\sqrt{7}\right)^2=13+2\sqrt{7}+7=20+2\sqrt{7}\)

e,\(\left(\sqrt{a}-\sqrt{b}\right)^2=a-2\sqrt{ab}+b\)

f,\(\left(\sqrt{3}-1\right)^2=3-2\sqrt{3}+1=4-2\sqrt{3}\)