数学计算题,八年级上(1)(5a+6b-7c)^2-(5a-6b+7c)^2 (2)(2x-3y-1)(2x+3y+1) (3)[-(1/2a^2x)^2+(1/3ax^2*ax)]÷(-1/6ax)(4)已知x^m=9,x^n=6.x^k=4求x^m-2n-2k (5)a^a-3=1,求a的可能值(6)若3x^2-x=1,求6x^3+7x-5x+2009
来源:学生作业帮助网 编辑:作业帮 时间:2024/08/31 05:02:21
数学计算题,八年级上(1)(5a+6b-7c)^2-(5a-6b+7c)^2 (2)(2x-3y-1)(2x+3y+1) (3)[-(1/2a^2x)^2+(1/3ax^2*ax)]÷(-1/6ax)(4)已知x^m=9,x^n=6.x^k=4求x^m-2n-2k (5)a^a-3=1,求a的可能值(6)若3x^2-x=1,求6x^3+7x-5x+2009
数学计算题,八年级上
(1)(5a+6b-7c)^2-(5a-6b+7c)^2 (2)(2x-3y-1)(2x+3y+1) (3)[-(1/2a^2x)^2+(1/3ax^2*ax)]÷(-1/6ax)
(4)已知x^m=9,x^n=6.x^k=4求x^m-2n-2k (5)a^a-3=1,求a的可能值(6)若3x^2-x=1,求6x^3+7x-5x+2009
数学计算题,八年级上(1)(5a+6b-7c)^2-(5a-6b+7c)^2 (2)(2x-3y-1)(2x+3y+1) (3)[-(1/2a^2x)^2+(1/3ax^2*ax)]÷(-1/6ax)(4)已知x^m=9,x^n=6.x^k=4求x^m-2n-2k (5)a^a-3=1,求a的可能值(6)若3x^2-x=1,求6x^3+7x-5x+2009
(1)(5a+6b-7c)^2-(5a-6b+7c)^2=【(5a+6b-7c)+(5a-6b+7c)】×【(5a+6b-7c)-(5a-6b+7c)】
=10a(12b-14c)=120ab-140ac
(2)(2x-3y-1)(2x+3y+1)=【2x-(3y+1)】×【2x+(3y+1)】=4x^2-(3y+1)^2=4x^2-9y^2-6y-1
(3)没看懂,另请高人吧!
(4)已知x^m=9,x^n=6.x^k=4求x^m-2n-2k
解x^(m-2n+2k)=x^m/(x^n)^2*(x^k)^2=9/36*16=4
(5)a^a-3=1 a^a-3×a^3=1×a^3 所以a^a=a^3 所以a=3
(6)你不小心打错数了吧,7x应为7x^2:若3x^2-x=1,求6x^3+7x^2-5x+2009
因为3x^2-x=1,所以3x^2=x+1
所以6x^3+7x^2-5x+2009
=x(6x^2+7x-5)+2009
=x(2x-1)(3x+5)+2009
=(2x-1)(3x^2+5x)+2009
=(2x-1)(1+x+5x)+2009
=(2x-1)(6x+1)+2009
=12x^2-4x-1+2009
=4(3x^2-x)+2008
=4*1+2008
=2012
(4)x的m-2n+2k次方就等于x的m次方除以x的2n次方再乘以x的2k次方 ,又于x的m次方=9,x的2n次方=36,x的2k次方=16,所以最终结果为9除以36再乘以16 结果为4
(5)a^a-3=1 a^a=4 所以a=2