解方程
6x+4×(10-x)=48
4x+48=7x-15
(60+70)x=(50+70)×(x+2)
(x+20)×2=2.5x+20
x-10=[2×(x-10)-9]×5
3200x+6000×(6-x)=26200.
解:(1)6x+4×(10-x)=48,
6x+40-4x=48,
2x+40-40=48-40,
2x=8,
2x÷2=8÷2,
x=4;
(2)4x+48=7x-15,
4x+48+15=7x-15+15,
4x+63-4x=7x-4x,
63=3x,
63÷3=3x÷3,
x=21;
(3)(60+70)x=(50+70)×(x+2),
130x=120x+240,
130x-120x=120x+240-120x,
10x=240,
10x÷10=240÷10,
x=24;
(4)(x+20)×2=2.5x+20,
2x+40=2.5x+20,
2x+40-2x=2.5x+20-2x,
40-20=20+0.5x-20,
20=0.5x,
20÷0.5=0.5x÷0.5,
x=40;
(5)x-10=[2×(x-10)-9]×5,
x-10=[2x-20-9]×5,
x-10=10x-145,
x-10+145=10x-145+145,
x+135-x=10x-x,
135=9x,
135÷9=9x÷9,
x=15;
(6)3200x+6000×(6-x)=26200,
3200x+36000-6000x=26200,
36000-2800x=26200,
36000-2800x+2800x=26200+2800x,
36000-26200=26200+2800x-26200,
9800=2800x,
9800÷2800=2800x÷2800,
x=3.5.
分析:(1)先化簡方程,再依據(jù)等式的性質(zhì),方程兩邊同時減40,再同時除以2求解,
(2)依據(jù)等式的性質(zhì),方程兩邊同時減4x,再同時加15,最后同時除以3求解,
(3)先化簡方程,再依據(jù)等式的性質(zhì),方程兩邊同時減120x,最后同時除以10求解,
(4)先化簡方程,再依據(jù)等式的性質(zhì),方程兩邊同時減2x,然后同時減20,最后同時除以0.5求解,
(5)先化簡方程,再依據(jù)等式的性質(zhì),方程兩邊同時加145,,然后同時減x,最后同時除以9求解,
(6)先化簡方程,再依據(jù)等式的性質(zhì),方程兩邊同時加2800x,然后同時減26200,最后同時除以2800求解.
點(diǎn)評:解方程的依據(jù)是等式的性質(zhì),對于能化簡的要依據(jù)等式的性質(zhì)先化簡,解答時注意對齊等號.