Question

помогите!!!!дам 20 баллов
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Answer 1

Ответ:

$4y {}^{2} - 5y - 21 = 0 \\ 4y {}^{2} + 7y - 12y - 21 = 0 \\ y(4y + 7) - 3(4y + 7) = 0\\(y - 3)(4y + 7) = 0 \\ y = 3 \\ y = - \frac{7}{4}$