Question

(B) x2 - 9x + 14 = 0​

Answer 1

$\Box \ \ \boxed{\begin{array}{l}\sf x^2-9x+14=0 \end{array}}\\\\\\a=1\\b=-9\\c=14$

$\Box \ \Delta=b^2-4.a.c\\\Box \ \Delta=(-9)^2-4.1.14\\\Box \ \Delta=81-56\\\boxed{\begin{array}{l}\sf \Delta=25 \end{array}}$

$\boxed{\begin{array}{l}\sf \ \ \ \ \ \ \ \ \ \ \ x=\dfrac{-b\pm\sqrt{\Delta}}{2.a}\\\\\\\ \ \ \ \ \ \ \ \ \ \ \ \ x=\dfrac{9\pm5}{2} \\\\\\---------------\\\\\\x'=\dfrac{9+5}{2} \ \ \ \ \ \ x'=\dfrac{14}{2} \ \ \ \ \ \ x'=7\\\\\\\\x''=\dfrac{9-5}{2} \ \ \ \ \ \ x''=\dfrac{4}{2} \ \ \ \ \ \ x''=2 \end{array}}$

$\boxed{\begin{array}{l}\sf S=\{2 \ , \ 7\} \end{array}}$

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