2
[a(a-c+b)+b(a+b-c)]/[a(b+c)+(b-c)(b+c)]=(a+b)(a-c+b)/((b+c)(a+b-c)=(a+b)(b+c)
3
[(a-2b)(a+2b)-5(a-2b)]/(a+2b-5)(a+2b+5)=(a-2b)(a+2b-5)/(a+2b+5)(a+2b-5)=
=(a-2b)/(a+2b+5)=(1,9-1,1)/(1,9+1,1+5)=0,8/8=0,1
4
2/3(3p-4q)-4/3(3p+3q)-4p/(3p-4q)(3p+4q)=
=(6p+8q-12p+16q-12p)/3(9p²-16q²)=(30q-24p)/3(9p²-16q²)=
=6(5q-4p)/3(9p²-16q²)=2(5q-4p)/(9p²-16q²)
5
(k+4)²/3k(5k+1) *(5k-1)(5k+1)/(4-k)(4+k)=(k+4)(5k-1)/3k(4-k)
6
1)1+(b²+c²-a²)/2bc=(2bc+b²+c²-a²)/2bc=[(b+c)²-a²]/2bc
2)1/a+1/(b+c)=(b+c+a)/a(b+c)
3)1/a-1/(b+c)=(b+c-a)/a(b+c)
4)(b+c+a)/a(b+c)*a(b+c)/(b+c-a)=(b+c+a)/(b+c-a)
5)(b+c+a)/(b+c-a)*(b+c+a)(b+c-a)/2bc=(b+c+a)²/2bc
7
1)(x+1)/(x-1)-(x-14)/(x+1)=(x²+2x+1-x²+2x-1)/(x²-1)=4x/(x²-1)
2)(x²+1)/(x²-1)-(x²-1)/(x²+1)=(x^4+2x²+1-x^4+2x²-1)/(x²-1)(x²+1)=
=4x²/(x²-1)(x²+1)
3)4x/(x²-1)*(x²-1)(x²+1)/4x²=(x²+1)/x
x=-3 3/4
[(-15/4)²+1]:(-15/4)=(225/16+1):*(-4/15)=-241/16*4/15=-241/60=-4 1/60
8
1)(1/c+1/d)^-1=[(c+d)/cd]^-1=cd/(c+d)
2)2d²-2c²=2(d-c)(d+c)
3)cd/(c+d)*2(d-c)(d+c)=2cd(d-c)