5x+3=2*4+(x-2)*6怎麼解方程?

5x+3=2*4+(x-2)*6怎麼解方程?


5x+3=8+6x-2*6
5x+3=8+6x-12
6x-5x=3+12-8
x=7



已知4x^2+7x-12=4,求-12x^2-21x的值.


因為4x^2+7x-12=4
所以4x^2+7x=16
則12x^2+21x=48
故-12x^2-21x=-48



已知4x²;+7x+2=4,求-12x²;-21x的值



4x²;+7x+2=4
4x²;+7x=2
∴-12x²;-21x
=-3(x²;+7x)
=-3×2
=-6



已知4x^2+7x-1=-3,求-12x^2-21x的值


4x²;+7x=-2
兩邊乘-3
-12x²;-21x=6