计算 (15 20:42:3)

题目

计算 (15 20:42:3)
1.23452 + 0.76552 + 2.469 x 0.7655               502 - 492 +482 -472 +````````+22 - 1                        
 
9X2 +6X =5X                             X2 = (3X+1)2

答案

1.2345² + 0.7655² + 2.469 x 0.7655
=1.2345² + 0.7655² + 2x1.2345 x 0.7655
=(1.2345+0.7655)²
=2²
=4
50² - 49² +48² -47² +````````+2² - 1
=(50+49)(50-49)+(48+47)(48-47)+……+(2+1)(2-1)
=(50+49)x1+(48+47)x1+……+(2+1)x1
=50+49+48+47+……+2+1
=(50+1)+(49+2)+……+(26+25)
=51*25
=204
9X² +6X =5X
9X²+X=0
X(9X+1)=0
X=0,X=-1/9
X²= (3X+1)²
X=3X+1或X=-(3X+1)
X=-1/2,X=-1/4