Предмет: Алгебра, автор: gabster54870976

Помогите плиз.Найти нули функции y=-x^2 +8x-7

Ответы

Автор ответа: Amigo3
1

Ответ: дискриминант 64-4*7=64-28=36. Корни х1=(-8+6)/(-2)=1, х2=(-8-6)/(-2)=7.

Объяснение:

Автор ответа: papagenius
1

Решение и ответ:

Нули функции — это значения аргумента, при которых функция равна нулю.

Для нахождения нулей функции решим квадратное уравнение.

\displaystyle y=-{x^2}+8x-7\\-{x^2}+8x-7=0\\D={b^2}-4ac={8^2}-4\cdot(-1)\cdot(-7)=64-28=36\\\\{x_{1;2}}=\frac{{-b\pm\sqrt D}}{{2a}}=\frac{{-8\pm\sqrt{36}}}{{2\cdot (-1)}}=\frac{{-8\pm6}}{{-2}}\\\\{x_1}=\frac{{-8+6}}{{-2}}=\frac{{-2}}{{-2}}=1\\\\{x_2}=\frac{{-8-6}}{{-2}}=\frac{{-14}}{{-2}}=7

Ответ: x₁ = 1; x₂ = 7.

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