1)=(17,31-12,69)(17,31+12,69)-(29,81-0,19)(29,81+0,19)=(4,62)30-(25,62)30=30(4,62-25,62)=30(-25)=-750..................2)=(7,84-12,16)(7,84+12,16)+(25,66-5,66)(25,66+5,66)=(-4,32)20+20(31,32)=20(-4,32+31,32)=20(-27)=-540
2x² - 9x + 4 = 0
D = b² - 4ac = 81 - 4 × 2 × 4 = 81 - 32 = 49 = 7²
x1 =( 9 + 7) / 4 = 4
x2 = ( 9 - 7) / 4 = 0,5
Ответ: x1 = 4, x2 = 0,5.