Question

(80-2x)*(60-2x)=3500怎么用配方法解?

Answer 1

(80-2x)*(60-2x)=3500

4x²-280x+4800=3500

4x²-280x+1300=0

x²-70x+650/2=0

x²-70x+35²-35²+650/2=0

(x-35)²=1225-650/2

x-35==±30

x=35=±30

x1=65 x2=5