-10x平方+1300x-30000=10000方程求解算半天算不出来用公式法根号里数开不出来配方法数字太大好像也算不出来

Question

-10x平方+1300x-30000=10000方程求解 算半天算不出来
用公式法 根号里数开不出来 配方法数字太大好像也算不出来

Answer 1

-10x" + 1300x - 30000 = 10000
- x" + 130x - 3000 = 1000
- x" + 130x - 4000 = 0
x" - 130x + 4000 = 0

分解因式
x" - 80x - 50x + 4000 = 0
x( x - 80 ) - 50( x - 80 ) = 0
( x - 80 )( x - 50 ) = 0

或者配方
x" - 130x + 65" - 4225 + 4000 = 0
( x - 65 )" - 225 = 0
( x - 65 )" - 15" = 0
( x - 65 - 15 )( x - 65 + 15 ) = 0
( x - 80 )( x - 50 ) = 0

解方程得
x1 = 80 ,
x2 = 50