3*х-2*y=4⇒y=(3*x-4)/2=1,5*x-2. То есть с=-2.
2)a)(7m-n)(7m+n)/-3mn(7m-n)=-(7m+n)3mn
b)(9x-4)(9x+4)/(9x+4)^2=(9x-4)/(9x+4)
3)(x-4)^2-25=(x-4)^2-5^2=(x-4-5)(x-4+5)=(x-9)(x+1)=0
1)x-9=0 2) x+1=0
x=9 x=-1
- х^3 + х(Х+2) = - х^3 +х( х^2 +4х +4)= - х^3 + х^3 +4х^2 +4х= 4х^2+4х =
= 4* (1/4)^2 + 4* 1/4 = 4 * 1/16 + 4*1/4= 1/4+1= 1 1/4 =1,25