Сделайте номер 702 (1,2,3)

$1) \frac{(x-b)(x-c)}{(a-b)(a-c)}- \frac{(x-c)(x-a)}{(a-b)(b-c)}- \frac{(x-a)(x-b)}{(a-c)(b-c)}=$ $\frac{(b-c)(x^{2}-xb-xc+bc)-(a-c)( x^{2} -xc-xa+ac)-(a-b)( x^{2}-xa-xb+ab )}{(a-b)(a-c)(b-c)}=$ $\frac{ x^{2}b-xb^{2}-xbc+ b^{2}c- x^{2} c+xbc+xc^{2}-bc^{2}- x^{2}a+xac+xa^{2}- a^{2}c+ x^{2}c-xc^{2}-xac+ac^{2}}{(a-b)(a-c)(b-c)}$ $*\frac{ - x^{2} a+xa^{2}+xab-a^{2}b+ x^{2}b-xab-xb^{2}+ab^{2}}{(a-b)(a-c)(b-c)}=$ $\frac{ 2x^{2} b-2xb^{2}+ b^{2}c-bc^{2}-2 x^{2}a-a^{2}c+ac^{2}+2xa^{2}-a^{2}b+ ab^{2}}{(a-b)(a-c)(b-c)}$

2. $\frac{1}{a- \frac{1}{ \frac{a- a^{2}-a}{1-a} } }= \frac{1}{ a- \frac{1-a}{- a^{2} } } = -\frac{ a^{2} }{- a^{3}-1+a}= \frac{a^{2}}{a^{3}-a+1 }$

3. $1+ \frac{1}{ 2+\frac{y}{3y+1} }=1+ \frac{3y+1}{6y+2+y}= \frac{7y+2+3y+1}{7y+2}= \frac{10y+3}{7y+2}$