Question

2 + 4 + 6 + ... + 2x = 10100

2 + 4 + 6 + ... + 2x = 2550

 

Answer 1

\(a,2+4+6+...+2x=10100\)

\(\Leftrightarrow\dfrac{2+2x}{2}:\left(\dfrac{2x-2}{2}+1\right)=10100\)

\(\Leftrightarrow\left(x+1\right).x=10100\)

\(\Leftrightarrow x^2+x=10100\)

\(\Leftrightarrow x^2+x-10100=0\)

\(\Leftrightarrow x=100\left(TM\right)\)

Tương tự câu a , ta có :

\(x^2+x=2550\)

\(\Leftrightarrow x^2+x-2550=0\)

\(\Leftrightarrow x=50\left(TM\right)\)