1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是( )2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( )3.若x^2+mx-15=(x+3)(x+n),则m的值是( )4.计算:3xy^2·(-2xy)=( )5.多项式(mx+8)(2-3x)展开后不含x项,则m=( )
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![1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是( )2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( )3.若x^2+mx-15=(x+3)(x+n),则m的值是( )4.计算:3xy^2·(-2xy)=( )5.多项式(mx+8)(2-3x)展开后不含x项,则m=( )](/uploads/image/z/15101710-70-0.jpg?t=1.%E8%AE%A1%E7%AE%97%3A%28-3%29%5E2n%2B1+%2B3%C2%B7%28-3%29%5E2n%28n%E6%98%AF%E6%AD%A3%E6%95%B4%E6%95%B0%29%E7%BB%93%E6%9E%9C%E6%AD%A3%E7%A1%AE%E7%9A%84%E6%98%AF%28+%292.%E8%AE%BE%285a%2B3b%29%5E2%3D%285a-3b%29%5E2%2BM%2C%E5%88%99M%E7%9A%84%E5%80%BC%E6%98%AF%28+%293.%E8%8B%A5x%5E2%2Bmx-15%3D%28x%2B3%29%28x%2Bn%29%2C%E5%88%99m%E7%9A%84%E5%80%BC%E6%98%AF%28+%294.%E8%AE%A1%E7%AE%97%3A3xy%5E2%C2%B7%28-2xy%29%3D%28+%295.%E5%A4%9A%E9%A1%B9%E5%BC%8F%28mx%2B8%29%282-3x%29%E5%B1%95%E5%BC%80%E5%90%8E%E4%B8%8D%E5%90%ABx%E9%A1%B9%2C%E5%88%99m%3D%28+%29)
1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是( )2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( )3.若x^2+mx-15=(x+3)(x+n),则m的值是( )4.计算:3xy^2·(-2xy)=( )5.多项式(mx+8)(2-3x)展开后不含x项,则m=( )
1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是( )
2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( )
3.若x^2+mx-15=(x+3)(x+n),则m的值是( )
4.计算:3xy^2·(-2xy)=( )
5.多项式(mx+8)(2-3x)展开后不含x项,则m=( )
1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是( )2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( )3.若x^2+mx-15=(x+3)(x+n),则m的值是( )4.计算:3xy^2·(-2xy)=( )5.多项式(mx+8)(2-3x)展开后不含x项,则m=( )
1.计算:(-3)^2n+1 +3·(-3)^2n(n是正整数)结果正确的是(0 )
2.设(5a+3b)^2=(5a-3b)^2+M,则M的值是( 60ab)
3.若x^2+mx-15=(x+3)(x+n),则m的值是( -2),n=-5
4.计算:3xy^2·(-2xy)=(-6x^2y^3 )
5.多项式(mx+8)(2-3x)展开后不含x项,则m=( 12)
=2mx-3mx^2+16-24x
2m-24=0
m=12
1.(-3)^2n+1 +3·(-3)^2n=9^n+1+3*9^n=4*9^n+1
2.(5a+3b)^2
=25a^2+9b^2+30ab
=25a^2+9b^2-30ab+60ab
=(5a-3b)^2+60ab
M=60ab
3.(x+3)(x+n)=x^2+(n+3)x+3n=x^2+mx-15
n+3=m (1)
3n...
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1.(-3)^2n+1 +3·(-3)^2n=9^n+1+3*9^n=4*9^n+1
2.(5a+3b)^2
=25a^2+9b^2+30ab
=25a^2+9b^2-30ab+60ab
=(5a-3b)^2+60ab
M=60ab
3.(x+3)(x+n)=x^2+(n+3)x+3n=x^2+mx-15
n+3=m (1)
3n=15 (2)
由(1)和(2)得n=5,m=8
4.3xy^2·(-2xy)=-6x^2 y^3
5.(mx+8)(2-3x)=-3mx^2+(2m-24)x+16
因展开后不含x项,故有2m-24=0
所以x=12
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