若4a的平方+9b的平方=13,3b-2a+5=0.则对于正整数n代数式,2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)的值?
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![若4a的平方+9b的平方=13,3b-2a+5=0.则对于正整数n代数式,2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)的值?](/uploads/image/z/1620959-23-9.jpg?t=%E8%8B%A54a%E7%9A%84%E5%B9%B3%E6%96%B9%2B9b%E7%9A%84%E5%B9%B3%E6%96%B9%3D13%2C3b-2a%2B5%3D0.%E5%88%99%E5%AF%B9%E4%BA%8E%E6%AD%A3%E6%95%B4%E6%95%B0n%E4%BB%A3%E6%95%B0%E5%BC%8F%2C2a%E7%9A%842n%2B4%E6%AC%A1%E6%96%B9%E4%B9%98%EF%BC%88b%E7%9A%842n%2B3%E6%AC%A1%E6%96%B9%2B2%E5%88%86%E4%B9%8B3%E4%B9%98b%E7%9A%842n%2B5%E6%AC%A1%E6%96%B9%EF%BC%89%E7%9A%84%E5%80%BC%3F)
若4a的平方+9b的平方=13,3b-2a+5=0.则对于正整数n代数式,2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)的值?
若4a的平方+9b的平方=13,3b-2a+5=0.
则对于正整数n代数式,2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)的值?
若4a的平方+9b的平方=13,3b-2a+5=0.则对于正整数n代数式,2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)的值?
4a^2+9b^2=13
3b-2a=-5
(3b-2a)^2=(-5)^2
4a^2-12ab+9b^2=25
13-12ab=25
ab=-1
2a^(2n+4)[b^(2n+3)+3b^(2n+5)/2]
=2a^(2n+4)b^(2n+3)+3a^(2n+4)b^(2n+5)
=2a*[a^(2n+3)b^(2n+3)]+3b[a^(2n+4)b^(2n+4)]
=2a*(ab)^(2n+3)+3b*(ab)^(2n+4)
=2a*(-1)^(2n+3)+3b*(-1)^(2n+4)
因为2n+3是奇数,2n+4是偶数
所以(-1)^(2n+3)=-1,(-1)^(2n+4)=1
所以原式=2a*(-1)+3b*1
=3b-2a=-5
a=1
b=-1
值为-4
若4a的平方+9b的平方=13,3b-2a+5=0。
则有a=1,b= -1
下面你会算了吧,呵呵
2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)
2a^(2n+4)*b(2n+3)*(3/2)b(2n+5)
4a^2+9b^=13
3b-2a+5=0
解出方程组的解(1,-1) (3/2,-2/3)
当a=1,b=-1时
2a^(2n+4)*[b^(2n+3)+(3/2)b^(2n+5)]=-5
当a=3/2,,b...
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2a的2n+4次方乘(b的2n+3次方+2分之3乘b的2n+5次方)
2a^(2n+4)*b(2n+3)*(3/2)b(2n+5)
4a^2+9b^=13
3b-2a+5=0
解出方程组的解(1,-1) (3/2,-2/3)
当a=1,b=-1时
2a^(2n+4)*[b^(2n+3)+(3/2)b^(2n+5)]=-5
当a=3/2,,b=-2/3
2a^(2n+4)*[b^(2n+3)+(3/2)b^(2n+5)]
=2a^(2n+4)*[b^(2n+3)(1+(3/2)b^2)]
=2a*a^(2n+3)*b^(2n+3)*[(1+(3/2)b^2)]
=2a*(ab)^(2n+3)*[(1+(3/2)b^2)]
=2(3/2)*(-1)*(5/3)
=-5
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