ppts.net
当前位置:首页>>关于(1)用配方法解方程:2x2-3x-1=0 (2)解...的资料>>

(1)用配方法解方程:2x2-3x-1=0 (2)解...

(1)x2-3x-2=0, x2-3x=2, x2-3x+94=2+94,(x-32)2=174, x-32=±172,x1=32+172=3+172,x2=32-172=3?172; (2)x2=4(2-x),x2+4x=8,x2+4x+4=12,(x+2)2=12,x+2=±2

(1)2x2-3x-1=0,2x2-3x=1,x2-32x=12,x2-32x+(34)2=12+(34)2,(x-34)2=1716x=3±174,x1=3+174,x2=3?174;(2)2x?3≥x+1 ①x?2>12(x+1) ②,由①得x≥4,由②得x>5,则原不等式组的解集为x>5;

题目应该是:2x² - 3x - 1 = 0 用配方法解方程 2x² - 3x - 1 = 0 x² - 3x/2 - 1/2 = 0 x² - 3x/2 + (3/4)² =1/2 +(3/4)² x² - 3x/2 + (3/4)² = 17/16 (x -3/4)² = 17 / 16 x -3/4 = ±√17 / 4 x = ...

(1)(2x-3)(x-1)=0,∴2x-3=0或x-1=0,∴x1=32,x2=1;(2)x2-32x=12,∴x2-32x+(34)2=(34)2+12,∴(x-34)2=1716,∴x-34=±174∴x1=3+174,x2=3-174.

(1)∵x 2 -4x=-1,∴x 2 -4x+4=3,∴(x-2) 2 =3,∴x-2=± 3 ,∴x 1 =2+ 3 ,x 2 =2- 3 ;(2)方程变形得3x 2 +10x+5=0,∵a=3,b=10,c=5,∴b 2 -4ac=10 2 -4×3×5=40,∴x= -10± 40 2×3 ,∴x 1 = -5+ 10 3 ,x 2 = -5- 10 3 ;(3)∵3(x-5) 2 ...

(1)∵2x2-4x-9=0,∴2x2-4x=9,∴x2-2x=92,∴x2-2x+1=92+1,∴(x-1)2=112,?x=1±222,解得x1=1+222,x2=1-222.(2)∵a=3,b=-43,c=2,∴b2-4ac=24,?x=43±242×3=23±63,解得x1=23+63,x2=23?63.

∵2x 2 +3x+1=0∴2x 2 +3x=-12(x 2 + 3 2 x)=-12(x 2 + 3 2 x+ 9 16 )=-1+ 9 8 ∴2(x+ 3 4 ) 2 = 1 8 即2(x+ 3 4 ) 2 - 1 8 =0故选B.

解:2x^2+1=3x 2x^2-3x+1=0 2(x^2-3/2*x+9/16-9/16)+1=0 2(x-3/4)^2-9/8+1=0 2(x-3/4)^2=1/8 (x-3/4)^2=1/16 x-3/4=1/4或-1/4 x=1或1/2

(1)由原方程,得2x2=24,∴x2=12,直接开平方,得x=±23,∴x1=23,x2=-23;(2)由原方程,得x2+4x=-1,等式的两边同时加上一次项系数一半的平方,得x2+4x+4=3,即(x+2)2=3;∴x+2=±3,∴x1=-2+3,x2=-2-3.

2x^2-3x=1 2(x^2-(3/2)x ) = 1 2[(x-3/4 )^2-9/16] = 1 (x-3/4 )^2-9/16 = 1/2 (x-3/4 )^2= 17/16 ans:A

网站首页 | 网站地图
All rights reserved Powered by www.ppts.net
copyright ©right 2010-2021。
内容来自网络,如有侵犯请联系客服。zhit325@qq.com