1:(x+1)(x+3)(x+5)(x+7)+152:x^2-2xy+y^2-13x+13y+303:先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.4:已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/20 14:59:10
![1:(x+1)(x+3)(x+5)(x+7)+152:x^2-2xy+y^2-13x+13y+303:先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.4:已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?](/uploads/image/z/121267-19-7.jpg?t=1%3A%28x%2B1%29%28x%2B3%29%28x%2B5%29%28x%2B7%29%2B152%3Ax%5E2-2xy%2By%5E2-13x%2B13y%2B303%3A%E5%85%88%E6%8A%8A4%28x%2B2z%29%28x-2z%29%2B12xy%2B9y%5E2%E5%88%86%E8%A7%A3%E5%9B%A0%E5%BC%8F%2C%E5%9C%A8%E6%B1%82%E5%80%BC%2C%E5%85%B6%E4%B8%ADx%EF%BC%9D1%2F2%2Cy%EF%BC%9D2%2F3%2Cz%EF%BC%9D3%2F4.4%3A%E5%B7%B2%E7%9F%A5a%2Cb%2Cc%E4%B8%BA%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%89%E8%BE%B9%2C%E4%B8%94a%2Cb%2Cc%E6%BB%A1%E8%B6%B3%28a%2Bb%2Bc%29%5E2%3D3%28a%5E2%2Bb%5E2%2Bc%5E2%29%EF%BC%8E%E9%97%AE%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E6%98%AF%E5%93%AA%E7%A7%8D%E4%B8%89%E8%A7%92%E5%BD%A2%3F)
1:(x+1)(x+3)(x+5)(x+7)+152:x^2-2xy+y^2-13x+13y+303:先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.4:已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?
1:
(x+1)(x+3)(x+5)(x+7)+15
2:
x^2-2xy+y^2-13x+13y+30
3:
先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.
4:
已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?
1:(x+1)(x+3)(x+5)(x+7)+152:x^2-2xy+y^2-13x+13y+303:先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.4:已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?
1.
(x+1)(x+3)(x+5)(x+7)+15
=[(x+1)(x+7)][(x+3)(x+5)]+15
=(x^2+8x+7)(x^2+8x+15)+15
=(x^2+8x+7)[(x^2+8x+7)+8]+15
=(x^2+8x+7)^2+8(x^2+8x+7)+15
=[(x^2+8x+7)+3][(x^2+8x+7)+5]
=(x^2+8x+10)(x^2+8x+12)
=(x^2+8x+10)(x+2)(x+6)
2.
x^2-2xy+y^2-13x+13y+30
=(x-y)^2-13(x-y)+30
=(x-y-3)(x-y-10)
3:
先把4(x+2z)(x-2z)+12xy+9y^2分解因式,在求值,其中x=1/2,y=2/3,z=3/4.
原式=4(x^2-4z^2)+12xy+9y^2=(4x^2+12xy+9y^2)-16z^2
=(2x+3y)^2-16z^2
=(2x+3y+4z)(2x+3y-4z)
=(1+2+3)(1+2-3)
=0
4:
已知a,b,c为三角形ABC三边,且a,b,c满足(a+b+c)^2=3(a^2+b^2+c^2).问三角形ABC是哪种三角形?
(A+B+C)^2=3(A^2+B^2+C^2)
A^2+B^2+C^2+2AB+2AC+2BC=3A^2+3B^2+3C^2
2AB+2AC+2BC=2A^2+2B^2+2C^2
A^2-2AB+B^2+A^2-2AC+C^2+B^2-2BC+C^2=0
(A-B)^2+(A-C)^2+(B-C)^2=0
A-B=0,A-C=0,B-C=0
A=B=C
等边三角形
1.
(x+1)(x+3)(x+5)(x+7)+15
=[(x+1)(x+7)][(x+3)(x+5)]+15
=(x^2+8x+7)(x^2+8x+15)+15
=(x^2+8x+7)[(x^2+8x+7)+8]+15
=(x^2+8x+7)^2+8(x^2+8x+7)+15
=[(x^2+8x+7)+3][(x^2+8x+7)+5] <...
全部展开
1.
(x+1)(x+3)(x+5)(x+7)+15
=[(x+1)(x+7)][(x+3)(x+5)]+15
=(x^2+8x+7)(x^2+8x+15)+15
=(x^2+8x+7)[(x^2+8x+7)+8]+15
=(x^2+8x+7)^2+8(x^2+8x+7)+15
=[(x^2+8x+7)+3][(x^2+8x+7)+5]
=(x^2+8x+10)(x^2+8x+12)
=(x^2+8x+10)(x+2)(x+6)
2.
x^2-2xy+y^2-13x+13y+30
=(x-y)^2-13(x-y)+30
=(x-y-3)(x-y-10)
3.把x,y,z 代入就可以了.方法和上两题一样.
4.两边展开,把能约的约掉,就可知道RT三角形.
不懂发消息问我.
收起