Đề bài: Phân tích đa thức thành nhân tử
a) 4x ² + 4x + 1=
b) (6x + 3) – (2x – 5) (2x + 1)=
c) (5x + 4) ² – 49x ²=
d) $x^{4}$ + 2$x^{3}$ – 2x – 4=
e) 15 xy ³ – 2yz – 15y ² + 6z=
f) 9 (2x+3) ² – 4(x+1) ²=
Đề bài: Phân tích đa thức thành nhân tử
a) 4x ² + 4x + 1=
b) (6x + 3) – (2x – 5) (2x + 1)=
c) (5x + 4) ² – 49x ²=
d) $x^{4}$ + 2$x^{3}$ – 2x – 4=
e) 15 xy ³ – 2yz – 15y ² + 6z=
f) 9 (2x+3) ² – 4(x+1) ²=
a) `4x^2+4x+1=(2x+1)^2`
b) `(6x+3)-(2x-5)(2x+1)`
`=3(2x+1)-(2x-5)(2x+1)`
`=-2(2x+1)(x+1)`
c) `(5x + 4)^2 – 49x^2`
`=(5x+4)^2-(7x)^2`
`=(5x+4-7x)(5x+4+7x)`
`=(-2x+4)(12x+4)`
d) `=x^4+2x^3-2x-4`
`=(x^4+2x^3)-(2x+4)`
`=x^3(x+2)-2(x+2)`
`=(x+2)(x^3-2)`
f) ` 9 (2x+3)^2 – 4(x+1)^2`
`=9(4x^2+12x+9) – 4(x^2+2x+1)`
`=36x^2+108x+81-4x^2-8x-4`
`=32x^2+100x + 77`
`=(32x^2 + 44x) + (56x + 77)`
`=4x(8x+11)+7(8x+11)`
`=(4x+7)(8x+11)`
a)4x² + 4x+1
=(2x)²+2.2x.1+1²
=(2x+1)²
b)(6x+3)-(2x-5)(2x+1)
=3(2x+1)-(2x-5)(2x+1)
=-2(2x+1)(x+1)
c)(5x+4)²-49x²
=(5x+4-7)(5x+4+7)
=(5x-3)(5x+11)
d)$x^{4}$ + 2x³ – 15y² + 6z
=x³(x+2)-x(x+2)
=x(x²-1)(x+2)
=x(x-1)(x+1)(x+2)
e)15xy³ – 2yz – 15y² + 6z=(câu này mk ko bt làm)
f)9(2x+3)² – 4(x+1)²=9(4x²+12x+9) – 4(x²+2x+1)
=36x²+108x+81-4x²-8x-4
=32x²+100x + 77
=(32x² + 44x) + (56x + 77)
=4x(8x+11)+7(8x+11)
=(4x+7)(8x+11)