Rút gọn biểu thức a, ( x+ 2y – 3z) ( x – 2y +3z ) b, (a + 1)(a+2) ( a^ + 4) (a-1) (a^ + 1) (a – 2) 03/09/2021 Bởi Jade Rút gọn biểu thức a, ( x+ 2y – 3z) ( x – 2y +3z ) b, (a + 1)(a+2) ( a^ + 4) (a-1) (a^ + 1) (a – 2)
`a) ( x+ 2y – 3z) ( x – 2y +3z )` `=[( x+ 2y)- 3z][( x – 2y)+3z]` `=(x+2y)^2-(3z)^2` `=x^2+4xy+4y^2-9z^2.` `b) (a + 1)(a+2) ( a^2 + 4) (a-1) (a^2 + 1) (a – 2)` `=[(a+1)(a-1)(a^2+1)][(a+2)(a-2)(a^2+4]` `=[(a^2-1)(a^2+1)][(a^2-4)(a^2+4)]` `=(a^4-1)(a^4-16)` `=a^8-16a^4-a^4+16` `=a^8-17a^4+16.` Bình luận
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`a) ( x+ 2y – 3z) ( x – 2y +3z )`
`=[( x+ 2y)- 3z][( x – 2y)+3z]`
`=(x+2y)^2-(3z)^2`
`=x^2+4xy+4y^2-9z^2.`
`b) (a + 1)(a+2) ( a^2 + 4) (a-1) (a^2 + 1) (a – 2)`
`=[(a+1)(a-1)(a^2+1)][(a+2)(a-2)(a^2+4]`
`=[(a^2-1)(a^2+1)][(a^2-4)(a^2+4)]`
`=(a^4-1)(a^4-16)`
`=a^8-16a^4-a^4+16`
`=a^8-17a^4+16.`