2корень2+корень50- корень98=2корень2+5корень2-7корень2=корень2
2) (3корень5-корень20)корень5=(3корень5-2корень5)=1корень5×корень5= корень25= 5
3)(корень3+корень2)2квадрате =3+2=5
X² + x - 1 = 0
D = 1² - 4 * 1 * (- 1) = 1 + 4 = 5
![x _{1} = \frac{-1+ \sqrt{5} }{2} \\\\x _{2} = \frac{-1- \sqrt{5} }{2}](https://tex.z-dn.net/?f=x+_%7B1%7D+%3D+%5Cfrac%7B-1%2B+%5Csqrt%7B5%7D+%7D%7B2%7D+%5C%5C%5C%5Cx+_%7B2%7D+%3D+%5Cfrac%7B-1-+%5Csqrt%7B5%7D+%7D%7B2%7D+)
<span> 700:100*7=49р - это скидка, а цена товара со скидкой 700-49=651р.</span>
<span>16 cos20 cos40 cos60 cos80=8 cos20cos40cos80=8cos20cos40cos80sin20/sin20=4sin40cos40cos80/sin20=2sin80cos80/sin20= sin160/sim20=sin(180-20)/sin20=sin20/sin20=1
соs60=1/2</span>