( 3,5 + 4,7 ) x 5,5   =   3,5 + 4,7 x 5,5            /S/

( 3,5 + 4,7 ) x 5,5     =   3,5 x 5,5 + 4,7 x 5,5         /Đ/

3,5 x 5,5 + 5,5 x 4,7       =   5,5 x ( 3,5 + 4,7 )       /Đ/

3,5 x 5,5 + 4,7    =   ( 3,5 + 4,7 ) x 5,5                        /S/

thanhk

Lời giải:

Ta có:

\(5,5+3\sqrt{2}=5,5+2\sqrt{\frac{9}{2}}=\frac{9}{2}+1+2\sqrt{\frac{9}{2}.1}=(\sqrt{\frac{9}{2}}+1)^2\)

\(\Rightarrow \sqrt{5,5+3\sqrt{2}}=\sqrt{\frac{9}{2}}+1\)

Tương tự:\(\sqrt{5,5-3\sqrt{2}}=\sqrt{\frac{9}{2}}-1\)

Do đó:

\(\frac{\sqrt{5,5+3\sqrt{2}}-\sqrt{5,5-3\sqrt{2}}}{6\sqrt{2}}=\frac{\sqrt{\frac{9}{2}}+1-(\sqrt{\frac{9}{2}}-1)}{6\sqrt{2}}\)

\(=\frac{2}{6\sqrt{2}}=\frac{1}{3\sqrt{2}}\)

\(\dfrac{\sqrt{5,5+3\sqrt{2}}-\sqrt{5,5-3\sqrt{2}}}{6\sqrt{2}}=\dfrac{\sqrt{2}\cdot\sqrt{5,5+3\sqrt{2}}-\sqrt{2}\cdot\sqrt{5,5-3\sqrt{2}}}{12}=\dfrac{\sqrt{11+2\cdot3\sqrt{2}}-\sqrt{11-2\cdot3\sqrt{2}}}{12}=\dfrac{\sqrt{9+2\cdot3\cdot\sqrt{2}+2}-\sqrt{9-2\cdot3\cdot\sqrt{2}+2}}{12}=\dfrac{\sqrt{\left(3+\sqrt{2}\right)^2}-\sqrt{\left(3-\sqrt{2}\right)^2}}{12}=\dfrac{3+\sqrt{2}-3+\sqrt{2}}{12}=\dfrac{2\sqrt{2}}{12}=\dfrac{\sqrt{2}}{6}\)

a)43,5.5,5-3,5.2,7+43,5.4,5-3,5.7.3

=(43,5.5,5+43,5.4,5)+(-3,5.2,7-3,5.7,3)

=43,5.(5,5+4,5)-3,5.(2,7+7,3)

=43,5.10-3,5.10

=435-35

=400

b)35²+40²-25²+40.70

=(35²-25²)+40²+40.70

=(35-25).(35+25)+40²+40.70

=10.60+40²+40.70

=600+1600+2800

=2200+2800

=5000

\(3,5\text{×}3,5+3,5+3,5\text{×}5,5\)

\(=3,5\text{×}3,5+3,5\text{×}1+3,5\text{×}5,5\)

\(=3,5\text{×}\left(3,5+1+5,5\right)\)

\(=3,5\text{×}10=35\)

Số số hạng là (127,5-1,5):2+1=64(số)

Tổng là (127,5+1,5)*64/2=4128

\(=\left(7,5+2,5\right)+\left(6,5+3,5\right)+\left(5,5+4,5\right)\\ =10+10+10=30\)

\(=\left(7,5+2.5\right)+\left(6,5+3,5\right)+\left(5,5+4,5\right)=10+10+10=30\)

=(7,5+2,5)+(6,5+3,5)+(5,5+4,5)

=10+10+10=30

=42 

ht nhé

đúng k và kb cho mink nhé

\(7,5+6,5+5,5+4,5+3,5+2,5=30\)

vj9