Đáp án:
x=100
Lời giải:
$\dfrac{x-90}{10}+$$\dfrac{x-76}{12}+$$\dfrac{x-58}{14}+$$\dfrac{x-36}{16}+$$\dfrac{x-15}{17}=15$
$⇔(\dfrac{x-90}{10}-1)+($$\dfrac{x-76}{12}-2)+($$\dfrac{x-58}{16}-3)+($$\dfrac{x-36}{16}-4)+($$\dfrac{x-15}{17}-5)=0$
$⇔\dfrac{x-100}{10}+$$\dfrac{x-100}{12}+$$\dfrac{x-100}{14}+$$\dfrac{x-100}{16}+$$\dfrac{x-100}{17}=0$
$⇔(x-100).(\dfrac{1}{10}+$$\dfrac{1}{12}+$$\dfrac{1}{14}+$$\dfrac{1}{16}+$$\dfrac{1}{17})=0$
$⇔x-100=0\text{ (Vì:}$$\dfrac{1}{10}+$$\dfrac{1}{12}+$$\dfrac{1}{14}+$$\dfrac{1}{16}+$$\dfrac{1}{17}$$\neq 0)$
$⇔x=100$
