Question

数学解方程

Answer 1

两边同取lg
则(lgx+2)lgx=lg1000=3
则(lgx)平方+2lgx -3=0
则(lgx+3)(lgx-1)=0
所以lgx+3=0或者lgx-1=0
所以lgx=-3或lgx=1
所以x=0.001或x=10

Answer 2

16/9X=4/3X=3/4X=105*5/6=19*5=953X=3.9X=1.3X=15除以5/6=18X=64X=7.5÷2=3.75x=5/8-5/16=5/16x=10÷3/5=50/3X=26/18-2/3+1/2=26/18-12/18+9/18=23/18X=30X=3/4*6/7*8/9=4/73/5X1/2-x=1/5X=1/10x+(1.5-1.2)=7=7-2.7X=4.3xX2/3=8X3/4X=6*3/2X=91/4+1/5x450.4x-1.6=18看不懂5x+18X6=128X=(128-108)÷5X=44x-15X2/3=12X=(12+10)÷4X=5.50.8÷x=5.4÷3X=0.8÷1.8=4/9

Answer 3

两边取以10为底的对数，(lgx+2)*lgx=lg1000,
(lgx)^2+2lgx-3=0,
(lgx+3)(lgx-1)=0,
lgx=-3, lgx=1,
x=0.001, x=10

Answer 4

(lgx+2)lgx=3
设lgx=y
(y+2)y=3
yy+2y-3=0
(y+3)(y-1)=0
y=-3 或 y=1
lgx=-3 或 lgx=1
x=1/1000 或 x=10.

Answer 5

请采纳

追问

lgx等于–3 x怎么算呢

追答

x=10 的-3次方

追问

哦！