Răspuns:
[tex]a) \frac{3}{5} = \frac{x}{10} \\ 5x = 3 \times 10 \\ 5x = 30 \\ x = 30 \div 5 \\ x = 6[/tex]
[tex]b) \frac{7}{x} = \frac{21}{15} \\ 21x = 7 \times 15 \\ 21x = 105 \\ x = 105 \div 21 \\ x = 5[/tex]
[tex]c) \frac{x + 2}{ {x + 7} } = \frac{3x + 6}{48} \\ (x + 2) \times 48 = (x + 7)(3x + 6) \\ 48x + 2 \times 48 = x \times 3x + x \times 6 + 7 \times 3x + 7 \times 6 \\ 48x + 96 = 3 {x}^{2} + 6x + 21x + 42 \\ 96 - 42 = 3 {x}^{2} + 6x - 48x + 21x \\ 54 = 3 {x}^{2} - 21x \\ 3 {x}^{2} - 21x + 54 = 0 | \div 3 \\ {x}^{2} - 7x + 18 = 0 \\ a = 1 \: b = - 7 \: c = 18 \\ delta \: = {b}^{2} - 4ac = ( - 7) ^{2} - 4 \times 1 \times 18 = 49 - 72 = - 23 \\ cum \: delta \: < 0 \: rezulta \: ca \: ecuatia \: nu \: are \: solutii \: reale \: [/tex]
La c) pune tu simbolul pentru delta
