1. x²-3x-4=0.
x²+x-4x-4=0.
x(x+1)-4(x+1)=0.
(x-4)(x+1)=0. x2=4. x2=-1.
2. 2x²+20=14x.
x²-7x+10=0.
x²-2x-5x+10=0.
x(x-2)-5(x-2)=0.
(x-2)(x-5)=0. x1=2. x2=5.
3. x²+8x+16=0.
x1,2=(-8±√(64-64))/2=-8/2.
x=-4.
4. 8x²-26x=7.
8x²-26x-7=0.
x1,2=(26±√(676+224))/16=(26±30)/16.
x1=7/2. x2=-1/4
5. 9x²-3x+1=0.
x1,2=(3±√(9-36))/18=(3±√-27))/18. ∅
6. 18x²-9x=0. 9x(2x-1)=0.
x1=0. x=1/2.
7. 6k²-6=0. k²=6/6. k=±1.