化简求值:(7a^2-4a)(5a^2-a-1)+(2-a ^2+4a),其中a=-3前面两个括号之间是乘号

化简求值:(7a^2-4a)(5a^2-a-1)+(2-a ^2+4a),其中a=-3前面两个括号之间是乘号
化简求值:(7a^2-4a)(5a^2-a-1)+(2-a ^2+4a),其中a=-3
前面两个括号之间是乘号

化简求值:(7a^2-4a)(5a^2-a-1)+(2-a ^2+4a),其中a=-3前面两个括号之间是乘号
(7a^2-4a)(5a^2-a-1)+(2-a ^2+4a)
=35a^4-7a³-7a²-20a³+4a²+4a+2-a²+4a
=35a^4-27a³-4a²+8a+2
当a=-3时,
原式=35*81+27*27-4*9-8*3+2
=3506

原式=35a^4-27a^3-4a^2+8a+2

2942
=63乘47-7-12
=2942

你检查原题，前面的两个括号之间是什么符号？

1/(x-4)(x-2)+1/x(x-2)+1/x(x+2)+1/(x+2)(x+4)
=1/(x-4)(x-2)+1/(x+2)(x+4)+1/x(x-2)+1/x(x+2)
=[(x+2)(x+4)+(x-4)(x-2)]/(x+2)(x-2)(x+4)(x-4)+ (x+2+x-2)/x(x+2)(x-2)
=(x^2+6x+8+x^2-6x+8)/(x^2-4)(x...

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1/(x-4)(x-2)+1/x(x-2)+1/x(x+2)+1/(x+2)(x+4)
=1/(x-4)(x-2)+1/(x+2)(x+4)+1/x(x-2)+1/x(x+2)
=[(x+2)(x+4)+(x-4)(x-2)]/(x+2)(x-2)(x+4)(x-4)+ (x+2+x-2)/x(x+2)(x-2)
=(x^2+6x+8+x^2-6x+8)/(x^2-4)(x^2-16) + 2/(x^2-4)
=(2x^2+16)/(x^2-4)(x^2-16)+2/(x^2-4)
=(2x^2+16+2(x^2-16))/(x^2-4)(x^2-16)
=(2x^2+16+2x^2-32)/(x^2-4)(x^2-16)
=(4x^2-16)/(x^2-4)(x^2-16)
=4(x^2-4)/(x^2-4)(x^2-16)
=4/(x^2-16)

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