ptđt a,x^2-x-56 b,5x^2-x-4 c,x^4+64 d,4x^4+1 e, 4x^4+81 g, 64x^4+y^4 19/10/2021 Bởi Raelynn ptđt a,x^2-x-56 b,5x^2-x-4 c,x^4+64 d,4x^4+1 e, 4x^4+81 g, 64x^4+y^4
Đáp án: Giải thích các bước giải: `a)x^2-x-56` `=x^2+7x-8x-56` `=x(x+7)-8(x+7)` `=(x-8)(x+7)` `b)5x^2-x-4` `=5x^2-5x+4x-4` `=5x(x-1)+4(x-1)` `=(5x+4)(x-1)` `c)x^4+64` `=x^4+16x^2+64-16x^2` `=(x^2+8)^2-(4x)^2` `=(x^2+8-4x)(x^2+8+4x)` `d)4x^4+1` `=4x^4+4x^2+1-4x^2` `=(2x^2+1)-(2x)^2` `=(2x^2+1-2x)(2x^2+1+2x)` `e)4x^4+81` `=4x^4+36x^2+81-36x^2` `=(2x^2+9)^2-(6x)^2` `=(2x^2+9-6x)(2x^2+9+6x)` `g)64x^4+y^4` `=64x^4+16x^2y^2+y^4-16x^2y^2` `=(8x^2+y^2)^2-(4xy)^2` `=(8x^2+y^2-4xy)(8x^2+y^2+4xy)` Bình luận
Đáp án+Giải thích các bước giải: \[a,x^2-x-56\\=x^2-8x+7x-56\\=x(x-8)+7(x-8)\\=(x-8)(x+7)\\b,5x^2-x-4\\=5x^2-5x+4x-4\\=5x(x-1)+4(x-1)\\=(x-1)(5x+4)\\c,x^4+64\\=x^4+2.x^2.8+64-16x^2\\=(x^2+8)^2-16x^2\\=(x^2-4x+8)(x^2+4x+8)\\d,4x^4+1\\=4x^4+4x^2+1-4x^2\\=(2x^2+1)^2-4x^2\\=(2x^2-2x+1)(2x^2+2x+1)\\e,4x^4+81\\=4x^4+2.2x^2.9+81-36x^2\\=(2x^2+9)^2-36x^2\\=(2x^2-6x+9)(2x^2+6x+9)\\g,64x^4+y^4\\=64x^4+2.8x^2y^2+y^4-16x^2y^2\\=(8x^2+y^2)^2-(4xy)^2\\=(8x^2-4xy+y^2)(8x^2+4xy+y^2)\] Bình luận
Đáp án:
Giải thích các bước giải:
`a)x^2-x-56`
`=x^2+7x-8x-56`
`=x(x+7)-8(x+7)`
`=(x-8)(x+7)`
`b)5x^2-x-4`
`=5x^2-5x+4x-4`
`=5x(x-1)+4(x-1)`
`=(5x+4)(x-1)`
`c)x^4+64`
`=x^4+16x^2+64-16x^2`
`=(x^2+8)^2-(4x)^2`
`=(x^2+8-4x)(x^2+8+4x)`
`d)4x^4+1`
`=4x^4+4x^2+1-4x^2`
`=(2x^2+1)-(2x)^2`
`=(2x^2+1-2x)(2x^2+1+2x)`
`e)4x^4+81`
`=4x^4+36x^2+81-36x^2`
`=(2x^2+9)^2-(6x)^2`
`=(2x^2+9-6x)(2x^2+9+6x)`
`g)64x^4+y^4`
`=64x^4+16x^2y^2+y^4-16x^2y^2`
`=(8x^2+y^2)^2-(4xy)^2`
`=(8x^2+y^2-4xy)(8x^2+y^2+4xy)`
Đáp án+Giải thích các bước giải:
\[a,x^2-x-56\\=x^2-8x+7x-56\\=x(x-8)+7(x-8)\\=(x-8)(x+7)\\b,5x^2-x-4\\=5x^2-5x+4x-4\\=5x(x-1)+4(x-1)\\=(x-1)(5x+4)\\c,x^4+64\\=x^4+2.x^2.8+64-16x^2\\=(x^2+8)^2-16x^2\\=(x^2-4x+8)(x^2+4x+8)\\d,4x^4+1\\=4x^4+4x^2+1-4x^2\\=(2x^2+1)^2-4x^2\\=(2x^2-2x+1)(2x^2+2x+1)\\e,4x^4+81\\=4x^4+2.2x^2.9+81-36x^2\\=(2x^2+9)^2-36x^2\\=(2x^2-6x+9)(2x^2+6x+9)\\g,64x^4+y^4\\=64x^4+2.8x^2y^2+y^4-16x^2y^2\\=(8x^2+y^2)^2-(4xy)^2\\=(8x^2-4xy+y^2)(8x^2+4xy+y^2)\]