计算:(2a+1)的2次方-(2a+1)(-1+2a) (2)(2x-3y)(3y+2x)-(4y-3x)(3x+4y)

问题描述:

计算:(2a+1)的2次方-(2a+1)(-1+2a) (2)(2x-3y)(3y+2x)-(4y-3x)(3x+4y)
(3)(-999*3分之2)的2次方 (4)-10*7分之2*9*7分之5

(1)(2a+1)^2-(2a+1)(-1+2a)
=(2a+1)[2a+1-(-1+2a)]
=(2a+1)(2)
=4a+2
(2)(2x-3y)(3y+2x)-(4y-3x)(3x+4y)
=(4x^2-9y^2)-(16y^2-9x^2)
=13x^2-25y^2
(3)(-999*3分之2)的2次方
(-999*(2/3))^2
=(-666)^2
=443556
(4)-10*7分之2*9*7分之5
10*(2/7)*9*(5/7)
=90*10/49
=900/49