Question

(2r-5)^2-4(y-3)^2-4y при y= -2/7

Answer 1

Ответ:

- 11.

Объяснение:

(2y-5)²- 4(y-3)² - 4y = 4y² - 20y + 25 - 4•(y² - 6y + 9) - 4y = 4y² - 20y + 25 - 4y² + 24y - 36 - 4y = - 11.

Значение выражения не зависит от значения переменной.

Answer 2

To evaluate the expression $(2r-5)^2 - 4(y-3)^2 - 4y$ when $y = -\frac{2}{7}$, we'll substitute $y$ with $-\frac{2}{7}$ and then simplify the expression step by step:

$y = -\frac{2}{7}$

Now substitute $y$ into the expression:

$$\begin{align*} (2r-5)^2 - 4\left(-\frac{2}{7} - 3\right)^2 - 4\left(-\frac{2}{7}\right) &= (2r-5)^2 - 4\left(-\frac{23}{7}\right)^2 + \frac{8}{7}\\ &= (2r-5)^2 - 4\left(\frac{23^2}{49}\right) + \frac{8}{7}\\ &= (2r-5)^2 - \frac{4 \times 529}{49} + \frac{8}{7}\\ &= (2r-5)^2 - \frac{2116}{49} + \frac{8}{7}\\ &= (2r-5)^2 - \frac{2116 + 392}{49}\\ &= (2r-5)^2 - \frac{2508}{49}\\ \end{align*}$$

Now we have the expression $(2r-5)^2 - \frac{2508}{49}$ when $y = -\frac{2}{7}$.