0,8=8/10=4/5 , 0,6=6/10=3/5 , 0,75=75/100=3/4 7*5 3*5 100 -----+--------- + --------- - 2 =0 4*x 4*3*x x² 35x+5x+100-2x² ---------------------- =0 4x² 2x²-40x-100=0 x²-20x-50=0 x₁=10-5√6 x₂=10+5√6