x1,x2,x3.xn的平均數為4則5x1+6,5x2+6…5xn+6的平均數是?(5x1+6是5乘x1加6) 要解釋清楚一點哦

x1,x2,x3.xn的平均數為4則5x1+6,5x2+6…5xn+6的平均數是?(5x1+6是5乘x1加6) 要解釋清楚一點哦


因為:
(x1+x2+x3+.+xn)/n=4
所以:
(5x1+6+5x2+6+5x3+.+xn)/n
=(5x1+5x2+…+5xn+6n)/n
=(5x1+5x2+…+5xn)/n+6n/n
=5(x1+x2+x3+…+xn)/n+6
=5*4+6
=26



分解因式:5x2-10x+5=______.


5x2-10x+5,=5(x2-2x+1),=5(x-1)2.



因式分解:5x2-15x3y+20xy2
5x的二次方减十五x的三次方y加20xy的二次方…


5x^2-15x^3y+20xy^2
=5x^2*1-5x*3^3y+5x*4y^2
=5x^2(1-3^3y+4^y2)