А) (√6+√5)²-√120=(√6²+2√6√5+√5²)-√(4*30)=6+2√30+5-2√30=11
б) √60+(√5-√3)²=√(4*15)+(√5²-2√5√3+√3²)=2√15+5-2√15+3=8
в)
![( \sqrt{2+\sqrt{3}}+\sqrt{2-\sqrt{3}})^{2} =(\sqrt{2+\sqrt{3}})^{2}+2\sqrt{2+\sqrt{3}}\sqrt{2- \sqrt{3}}+](https://tex.z-dn.net/?f=%28+%5Csqrt%7B2%2B%5Csqrt%7B3%7D%7D%2B%5Csqrt%7B2-%5Csqrt%7B3%7D%7D%29%5E%7B2%7D+%3D%28%5Csqrt%7B2%2B%5Csqrt%7B3%7D%7D%29%5E%7B2%7D%2B2%5Csqrt%7B2%2B%5Csqrt%7B3%7D%7D%5Csqrt%7B2-+%5Csqrt%7B3%7D%7D%2B)
![( \sqrt{2- \sqrt{3}})^{2}=2+ \sqrt{3} +2\sqrt{(2+ \sqrt{3})(2- \sqrt{3}})+2- \sqrt{3} =](https://tex.z-dn.net/?f=%28+%5Csqrt%7B2-+%5Csqrt%7B3%7D%7D%29%5E%7B2%7D%3D2%2B+%5Csqrt%7B3%7D+%2B2%5Csqrt%7B%282%2B+%5Csqrt%7B3%7D%29%282-+%5Csqrt%7B3%7D%7D%29%2B2-+%5Csqrt%7B3%7D+%3D)
![4+2 \sqrt{2^{2}-\sqrt{3}^{2}}=4+2\sqrt{4-3} =4+2 \sqrt{1}=5](https://tex.z-dn.net/?f=4%2B2+%5Csqrt%7B2%5E%7B2%7D-%5Csqrt%7B3%7D%5E%7B2%7D%7D%3D4%2B2%5Csqrt%7B4-3%7D+%3D4%2B2+%5Csqrt%7B1%7D%3D5)
г)
![( \sqrt{3+2\sqrt{2}}-\sqrt{3-2\sqrt{2}})^{2}=](https://tex.z-dn.net/?f=%28+%5Csqrt%7B3%2B2%5Csqrt%7B2%7D%7D-%5Csqrt%7B3-2%5Csqrt%7B2%7D%7D%29%5E%7B2%7D%3D)
![3+2\sqrt{2}-2\sqrt{(3+2\sqrt{2})(3-2\sqrt{2})}+3-2\sqrt{2}=6-2\sqrt{3^{2}-(2 \sqrt{2})^{2}}=](https://tex.z-dn.net/?f=3%2B2%5Csqrt%7B2%7D-2%5Csqrt%7B%283%2B2%5Csqrt%7B2%7D%29%283-2%5Csqrt%7B2%7D%29%7D%2B3-2%5Csqrt%7B2%7D%3D6-2%5Csqrt%7B3%5E%7B2%7D-%282+%5Csqrt%7B2%7D%29%5E%7B2%7D%7D%3D)
![6-2 \sqrt{9-4*2}=6-2* \sqrt{1} =6-2=4](https://tex.z-dn.net/?f=6-2+%5Csqrt%7B9-4%2A2%7D%3D6-2%2A+%5Csqrt%7B1%7D+%3D6-2%3D4)
х²-3=(х+√3)(х-√3)
4у²-5=(2у+√5)(2у-√5)
2-с²=(√2+с)(√2-с)
4-а=(2+√а)(2-√а)
![\frac{ x^{2} -2}{x+ \sqrt{2} }= \frac{(x+ \sqrt{2})(x- \sqrt{2})}{x+ \sqrt{2}}=x- \sqrt{2}](https://tex.z-dn.net/?f=+%5Cfrac%7B+x%5E%7B2%7D+-2%7D%7Bx%2B+%5Csqrt%7B2%7D+%7D%3D+%5Cfrac%7B%28x%2B+%5Csqrt%7B2%7D%29%28x-+%5Csqrt%7B2%7D%29%7D%7Bx%2B+%5Csqrt%7B2%7D%7D%3Dx-+%5Csqrt%7B2%7D)
![\frac{x-4}{ \sqrt{x} +2}= \frac{( \sqrt{x} +2)( \sqrt{x} -2)}{ \sqrt{x} +2} = \sqrt{x} -2](https://tex.z-dn.net/?f=+%5Cfrac%7Bx-4%7D%7B+%5Csqrt%7Bx%7D+%2B2%7D%3D+%5Cfrac%7B%28+%5Csqrt%7Bx%7D+%2B2%29%28+%5Csqrt%7Bx%7D+-2%29%7D%7B+%5Csqrt%7Bx%7D+%2B2%7D+%3D+%5Csqrt%7Bx%7D+-2)
![\frac{a- \sqrt{a} }{ \sqrt{a}-1 }= \frac{ \sqrt{a}( \sqrt{a}-1)}{ \sqrt{a}-1} = \sqrt{a} ](https://tex.z-dn.net/?f=+%5Cfrac%7Ba-+%5Csqrt%7Ba%7D+%7D%7B+%5Csqrt%7Ba%7D-1+%7D%3D+%5Cfrac%7B+%5Csqrt%7Ba%7D%28+%5Csqrt%7Ba%7D-1%29%7D%7B+%5Csqrt%7Ba%7D-1%7D+%3D+%5Csqrt%7Ba%7D+%0A)
![\frac{c \sqrt{c}+c}{c+ \sqrt{c} } = \frac{ \sqrt{c}(c+ \sqrt{c)}}{c+ \sqrt{c} } = \sqrt{c}](https://tex.z-dn.net/?f=+%5Cfrac%7Bc+%5Csqrt%7Bc%7D%2Bc%7D%7Bc%2B+%5Csqrt%7Bc%7D+%7D+%3D+%5Cfrac%7B+%5Csqrt%7Bc%7D%28c%2B+%5Csqrt%7Bc%29%7D%7D%7Bc%2B+%5Csqrt%7Bc%7D+%7D+%3D+%5Csqrt%7Bc%7D+)
в/(а²-в²) : в/(а²+ав) =
= в/(а-в)(а+в) : в/(а+в)*а =
= в/(а-в)(а+в) * (а+в)*а/в = а/(а-в),
при а = 1,1, в = 0,9: 1,1 / (1,1-0,9) = 1,1/0,2 = 5,5
640+х=900 <span>
y=720-380
y=340
</span><span> 640+х=900
</span>x=900-640
x=260
30+24+42=96 км весь путь
30:96=5/16 части в 1 час
24:96=1/4 часть во 2 час
42:96=7/16 части в 3 час