Question

Алгебра 8 класс очень нужна помощь​

Answer 1

Ответ:

1)

$25x^{2} +30x+9=0\\D=b^{2} -4ac= 900 - 4*25*9=900-900=0\\x=\frac{-b}{2a}=\frac{-30}{50} =\frac{-3}{5}=-\frac{3}{5}$

2)

$-2x^{2} +7x=0\\-x(2x-7)=0\\x(2x-7)=0\\x=0\\\\2x-7=0\\\\x1=0\\x2=3.5$

3)

$3x^{2} -11x-4=0\\3x^{2} +x-12x-4=0\\x(3x+1)-4(3x+1)=0\\(3x+1)-(x-4)=0\\3x+1=0\\x-4=0\\\\x1 = -\frac{1}{3} \\x2=4$

4)

$-\frac{1}{4}x^{2} +2x-4=0\\-x^{2} +8x-16=0\\x^{2} -8x+16=0\\(x-4)^{2}=0\\x=4$