如图,已知R=5.6,r=1.4,求圆环的面积（π取3.14）.分解因式：⑴3a^2+12ab+12b^2⑵(2x-y)^2-10(2x-y)+25⑶8ax^2+16a^2x+8a^3⑷-6x^2y-3x^3-3xy^2分解因式：⑴x^2+3x-4⑵x^2-3x-4⑶x^2+8x-20⑷x^2-5x-24⑸x^2+12x+27⑹x^2-8x

Question

如图,已知R=5.6,r=1.4,求圆环的面积（π取3.14）.
分解因式：
⑴ 3a^2+12ab+12b^2
⑵ (2x-y)^2-10(2x-y)+25
⑶ 8ax^2+16a^2 x+8a^3
⑷ -6x^2 y-3x^3-3xy^2
分解因式：
⑴ x^2+3x-4
⑵ x^2-3x-4
⑶ x^2+8x-20
⑷ x^2-5x-24
⑸ x^2+12x+27
⑹ x^2-8x+12
分解因式：
⑴ x^2+6xy-16y^2
⑵ x^2-11xy+24y^2
⑶ x^4+13x^2+36
⑷ ax^4-14ax^2-32a
⑸ (a+b)^2-15(a+b)+56
⑹ (a^2+a)^2-8(a^2+a)+12
填空：
⑴ 2(a+b)+3a(a+b)=( )(a+b)
⑵ x(a-b)-y(a-b)=(a-b)( )
⑶ –(x-y)^2-(x-y)=-(x-y)( )
分解因式：
⑴ ab-ac+b-c
⑵ a^2-ab-2a+2b
⑶ 3a-9b+2ac-6bc
⑷ 3x^2y+6xy-4x-8
分解因式：
⑴ x^2+3y-xy-3x
⑵ x^3+2x^2y-9x-18y
⑶ (y+2)x^2+(y+2)x-12y-24
⑷ m^2x^2+n^2y^2-m^2y^2-n^2x^2

Answer 1

如图,已知R=5.6,r=1.4,求圆环的面积（π取3.14）.
S=π(5.6^2-1.4^2)=π*29.4=92.316
分解因式：
⑴ 3a^2+12ab+12b^2
=3(a^2+4ab+4b^2)
=3(a+b)^2
⑵ (2x-y)^2-10(2x-y)+25
=(2x-y-5)^2
⑶ 8ax^2+16a^2 x+8a^3
=8a(x^2+2ax+a^2)
=8a(x+a)^2
⑷ -6x^2 y-3x^3-3xy^2
=-3x(x^2+2xy+y^2)
=-3x(x+y)^2
分解因式：
⑴ x^2+3x-4
=(x+4)(x-1)
⑵ x^2-3x-4
=(x-4)(x+1)
⑶ x^2+8x-20
=(x+10)(x-2)
⑷ x^2-5x-24
=(x-8)(x+3)
⑸ x^2+12x+27
=(x+3)(x+9)
⑹ x^2-8x+12
=(x-2)(x-6)
分解因式：
⑴ x^2+6xy-16y^2
=(x-2y)(x+8y)
⑵ x^2-11xy+24y^2
=(x-8y)(x-3y)
⑶ x^4+13x^2+36
=(x^2+4)(x^2+9)
⑷ ax^4-14ax^2-32a
=a(x^4-14x^2-32)
=a(x^2-16)(x^2+2)
=a(x+4)(x-4)(x^2+2)
⑸ (a+b)^2-15(a+b)+56
=(a+b-7)(a+b-8)
⑹ (a^2+a)^2-8(a^2+a)+12
=(a^2+a-6)(a^2+a-2)
=(a+3)(a-2)(a+2)(a-1)
填空：
⑴ 2(a+b)+3a(a+b)=( 2+3a )(a+b)
⑵ x(a-b)-y(a-b)=(a-b)(x-y )
⑶ –(x-y)^2-(x-y)=-(x-y)(x-y+1 )
分解因式：
⑴ ab-ac+b-c
=a(b-c)+b-c
=(b-c)(a+1)
⑵ a^2-ab-2a+2b
=a(a-b)-2(a-b)
=(a-2)(a-b)
⑶ 3a-9b+2ac-6bc
=3(a-3b)+2c(a-3b)
=(3+2c)(a-3b)
⑷ 3x^2y+6xy-4x-8
=3xy(x+2)-4(x+2)
=(x+2)(3xy-4)
分解因式：
⑴ x^2+3y-xy-3x
=x(x-y)-3(x-y)
=(x-y)(x-3)
⑵ x^3+2x^2y-9x-18y
=x^2(x+2y)-2(x+2y)
=(x^2-2)(x+2y)
⑶ (y+2)x^2+(y+2)x-12y-24
=(y+2)x(x+1)-12(y+2)
=(y+2)(x^2+x-12)
=(y+2)(x-3)(x+4)
⑷ m^2x^2+n^2y^2-m^2y^2-n^2x^2
=m^2(x^2-y^2)-n^2(x^2-y^2)
=(m+n)(m-n)(x+y)(x-y)