2 x квадрат-7x-4=0 4xквадрат-3x-1=0

Решите задачу:

$2 x^{2} -7x-4=0\\D=b ^{2} -4ac=(-7)^{2} -4*(-4)*2=49+32=81\\ \sqrt{D} =9\\ x_{2} = \frac{-b+ \sqrt{D} }{2a} = \frac{7+9}{2*2} = \frac{16}{4} =4\\x_{2} = \frac{-b- \sqrt{D} }{2a} = \frac{7-9}{2*2} = \frac{-2}{4} =- \frac{1}{2} \\$

$4 x^{2} -3x-1=0\\D=9+16=25\\ \sqrt{D} =5\\ x_{1} = \frac{3+5}{8} = \frac{8}{8} =1\\ x_{2} = \frac{3-5}{8} =- \frac{2}{8} = \frac{1}{4}$