2乘X平方+3=7X 2x^2+3=7x 2x^2-7x+3=0 x^2-(7/2)x+3/2=0 x^2-(7/2)x=-3/2 x^2-(7/2)x+(7/4)^2=-3/2+(7/4)^2 (x-7/4)^2=-3/2+49/16 (x-7/4)^2=-24/16+49/16 (x-7/4)^2=25/16 (x-7/4)^2=(5/4)^2 x-7/4=±(5/4) x=7/4±(5/4) x1=7/4+5/4=12/4=3 x2=7/4-5/4=1/2 2乘X平方+3=7X 2x^2+3=7x 2x^2-7x+3=0 x^2-(7/2)x+3/2=0 x^2-(7/2)x=-3/2 x^2-(7/2)x+(7/4)^2=-3/2+(7/4)^2 (x-7/4)^2=-3/2+49/16 (x-7/4)^2=-24/16+49/16 (x-7/4)^2=25/16 (x-7/4)^2=(5/4)^2 x-7/4=±(5/4) x=7/4±(5/4) x1=7/4+5/4=12/4=3 x2=7/4-5/4=1/2