1.
x²+2x=16x-49
x²-14x+49=0
x²-7x-7x+49=0
x(x-7)-7(x-7)=0
(x-7)(x-7)=0
(x-7)²=0
x=7
2.
x(2x+1)=3x+4
2x²+x=3x+4
2x²-2x-4=0
x²-x-2=0
x²+x-2x-2=0
x(x+1)-2(x+1)=0
(x-2)(x+1)=0
x=2 ∨ x=-1
3.
6/(x+5)=4/(3-4) ⇐ 3-4 ???
4.
6/x+6/(x+1)=5 |*x(x+1)
6(x+1)+6x=5x(x+1)
6x+6+6x=5x²+5x
5x²-7x-6=0
5x²-10x+3x-6=0
5x(x-2)+3(x-2)=0
(5x+3)(x-2)=0
5x+3=0
5x=-3
x=-3/5 ∨ x=2