ppi93gk88d的部落格

標題:

因式分解!!!!

發問:

1) a.512-a^3 b.9x^2-42xy+49y^2 c.(2x-1)^2-25 d.50-8y^2 e.8x^2-38x+35 f.20-7x-6x^2 g.-343-8y^3 h.(x+y)^3-8(x-y)^3

最佳解答:

• 一題中一數學選擇題Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! --(@1@
• electric circiut
• NDS太鼓之達人的初、中、高級玩的game都是一樣嗎？只有30幾隻歌嗎？@1@

• 一題中一數學選擇題Help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! --(@1@
• electric circiut
• NDS太鼓之達人的初、中、高級玩的game都是一樣嗎？只有30幾隻歌嗎？@1@

 

此文章來自奇摩知識+如有不便請留言告知

1a) 512 - a3 = 83 – a3 = ( 8 – a )( 64 + 8a + a2 ) {因 a3 – b3 = ( a – b )( a2 + ab + b2 )} b) 9x2 - 42xy + 49y2 = ( 3x )2 – 2 ( 3x )( 7y ) + ( 7y )2 = ( 3x – 7y )2 {因 ( a – b )2 = a2 – 2ab + b2 } c) ( 2x – 1 )2 – 25 = ( 2x – 1 )2 - 52 = { ( 2x – 1 ) + 5 }{ ( 2x – 1 ) – 5 } {因( a + b )( a – b ) = a2 – b2 } = ( 2x – 1 + 5 )( 2x – 1 – 5 ) = ( 2x + 4 )( 2x – 6 ) = 2 ( x + 2 ) 2 ( x – 3 ) = 4 ( x + 2 )( x – 3 ) d) 50 - 8y2 = 2 ( 25 – 4y2 ) = 2 { 52 – ( 2y )2 } = 2 ( 5 + 2y )( 5 – 2y ) e) 8x2 - 38x + 35 = ( 4x – 5 )( 2x – 7 ) {十字相乘法} f) 20 - 7x - 6x2 = - ( 6x2 + 7x – 20 ) = - ( 2x + 5 )( 3x – 4 ) g) - 343 - 8y3 = - {73 + ( 2y )3 } = - ( 7 + 2y )( 49 – 14y + 4y2 ) {因a3 + b3 = ( a + b )( a2 – ab + b2 ) h) ( x + y )3 – 8 ( x – y )3 = ( x + y )3 – { 2 ( x – y ) }3 = { ( x + y ) - 2 ( x – y ) }{ ( x + y )2 + 2 ( x + y )( x – y ) + 4 ( x – y )2 } = ( x + y – 2x + 2y )( x2 + 2xy + y2 + 2x2 – 2y2 + 4 ( x2 – 2xy + y2 )) = ( - x + 3y )( x2 + 2xy + y2 + 2x2 – 2y2 + 4x2 – 8xy + 4y2 ) = ( - x + 3y )( 7x2 – 6xy + 3y2 ) = - ( x – 3y )( 7x2 – 6xy + 3y2 )

其他解答:

a^2-b^2=(a+b)(a-b) a^3-b^3=(a-b)(a^2+ab+b^2) 用來用去二個等式 自己試試!