A)5x^2 - 9x - 2 = 0
D = b^2 - 4ac = (-9)^2 - 4·5·(-2) = 81 + 40 = 121
x1 = (9 - √121)/2·5 = (9 - 11)/10 = -2/10 = -0.2
x2 = (<span><span>9 + √121)/</span>2·5</span> = (<span>9 + 11)/10</span> = <span>20/10</span> = 2
б)2x^2 + 3x - 2 = 0
D = b^2 - 4ac = 3^2 - 4·2·(-2) = 9 + 16 = 25
x1 = (<span><span>-3 - √25)/</span>2·2</span> = (<span>-3 - 5)/4</span> = <span>-8/4</span> = -2
x2 = (<span><span>-3 + √25)/</span>2·2</span> = (<span>-3 + 5)/4</span> = <span>2/4</span> = 0.5
в)2x^2 + 7x + 3 = 0
D = b^2 - 4ac = 7^2 - 4·2·3 = 49 - 24 = 25
x1 = (-7 - √25)/2·2 = (-7 - 5)/4 = -12/4 = -3
x2 = (<span><span>-7 + √25)/</span>2·2</span> = (<span>-7 + 5)/4</span> = <span>-2/4</span> = -0.5
г)5x^2 - 8x - 4 = 0
D = b^2 - 4ac = (-8)^2 - 4·5·(-4) = 64 + 80 = 144
x1 = (<span><span>8 - √144)/</span>2·5</span> = (<span>8 - 12)/10</span> = <span>-4/10</span> = -0.4
x2 = (<span><span>8 + √144)/</span>2·5</span> = (<span>8 + 12)/10</span> = <span>20/10</span> = 2