Question

(7у+21)(1,8-0,3у) =0

Answer 1

Ответ:

-3

Пошаговое объяснение:

12,6y-2,1y+37,8-6,3=0

10,5y+31,5=0

10,5y= -31,5

y= -3

Answer 2

To solve the equation (7у+21)(1.8-0.3у) = 0, we need to find the values of у that make the equation true.

First, let's expand the expression:

(7у + 21)(1.8 - 0.3у) = 0

Multiply each term in the first parentheses by each term in the second parentheses:

(7у)(1.8) + (7у)(-0.3у) + (21)(1.8) + (21)(-0.3у) = 0

Simplify each term:

12.6у - 2.1у^2 + 37.8 - 0.9у = 0

Rearrange the terms in descending order of degree:

-2.1у^2 + 11.7у + 37.8 = 0

Now, we have a quadratic equation in the form of aу^2 + bу + c = 0, where:

a = -2.1 b = 11.7 c = 37.8

To solve this quadratic equation, we can use the quadratic formula:

у = (-b ± √(b^2 - 4ac)) / (2a)

Substituting the values of a, b, and c into the formula:

у = (-(11.7) ± √((11.7)^2 - 4(-2.1)(37.8))) / (2(-2.1))

Calculating the discriminant:

D = (11.7)^2 - 4(-2.1)(37.8)

D = 136.89 + 319.44

D = 456.33

Since the discriminant is positive, there are two distinct real solutions. Calculating the solutions:

у = (-11.7 ± √456.33) / (-4.2)

у = (-11.7 ± 21.37) / (-4.2)

For the positive square root:

у = (-11.7 + 21.37) / (-4.2)

у = 9.67 / (-4.2)

у ≈ -2.30

For the negative square root:

у = (-11.7 - 21.37) / (-4.2)

у = -33.07 / (-4.2)

у ≈ 7.87

Therefore, the solutions to the equation (7у+21)(1.8-0.3у) = 0 are у ≈ -2.30 and у ≈ 7.87.