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
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![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](/uploads/image/z/444735-63-5.jpg?t=%E6%95%B0%E5%AD%A6%E8%AE%A1%E7%AE%97%E9%A2%98%2C%E5%85%AB%E5%B9%B4%E7%BA%A7%E4%B8%8A%EF%BC%881%EF%BC%89%285a%2B6b-7c%29%5E2-%285a-6b%2B7c%29%5E2+++%EF%BC%882%29%EF%BC%882x-3y-1%29%282x%2B3y%2B1%29++++%283%29%5B-%281%2F2a%5E2x%29%5E2%2B%281%2F3ax%5E2%2Aax%29%5D%C3%B7%EF%BC%88-1%2F6ax%29%284%29%E5%B7%B2%E7%9F%A5x%5Em%3D9%2Cx%5En%3D6.x%5Ek%3D4%E6%B1%82x%5Em-2n-2k++%285%29a%5Ea-3%3D1%2C%E6%B1%82a%E7%9A%84%E5%8F%AF%E8%83%BD%E5%80%BC%EF%BC%886%EF%BC%89%E8%8B%A53x%5E2-x%3D1%2C%E6%B1%826x%5E3%2B7x-5x%2B2009)
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