Question

х²+х-а=0. если х1=4
по теореме Виета​

Answer 1

${x}^{2} + x- a = 0 \\ x_{1} + x_{2} = - 1 \\ x_{1} \times x_{2} = - a \\ \\ 4x_{2} = - a \\ 4+ x_{2} = - 1 \\ \\ x_{2} = - 5 \\ 4 \times ( - 5) = - a \\ \\ - 20 = - a \\ a = 20$