1)3x²+3=10x 2)2x²-9x-10=0
3x²-10x+3=0 D=81+80=161
D=100-36=64 x₁=9+√161/4=9+√23·7/4=9+√9·3·7/4=9+3√21/4
x₁=3, x₂=2/6=1/3. x₂=9-3√21/4.
3)x²-2x-9=0 4)x²-x-1=0 5)(x+2)²+(x-3)²=13
D=4+36=40 D=1+4=5 x²+4x+4+x²-6x+9-13=0
x₁=2+√40/2=2+2√5/2=1+2√5 x₁=1+√5/2 2x²-2x=0
x₂=1-2√5. x₂=1-√5/2. 2x·(x-1)=0
2x=0 или x-1=0
x=0 x=1.