Câu hỏi của Tran inh Toan

Question

Tìm x biết:

2+4+6+8+...+2x = 10100

Nho cac ban huong dan giai giup bai nay

Mạc Thu Hà · Accepted Answer

A=2(1+2+3+.........+x)=10100

suy ra 1+2+3+.................+x=5050

$\frac{x\left(x+1\right)}{2}$=5050 $\Rightarrow$x²+x=10100$\Rightarrow$x²+x-10100=0$\Rightarrow$x=100 hoac x=-101 ma x>0 nen x=100

Câu trả lời:

A=2(1+2+3+.........+x)=10100

suy ra 1+2+3+.................+x=5050

$\frac{x\left(x+1\right)}{2}$=5050 $\Rightarrow$x²+x=10100$\Rightarrow$x²+x-10100=0$\Rightarrow$x=100 hoac x=-101 ma x>0 nen x=100