若2m=3,4n=8,则23m-2n+3的值是______.
题型:填空题难度:简单来源:不详
若2m=3,4n=8,则23m-2n+3的值是______. |
答案
∵2m=3,4n=8, ∴23m-2n+3=(2m)3÷(2n)2×23, =(2m)3÷4n×23, =33÷8×8, =27. 故填27. |
举一反三
判断下面的计算对不对 (1)b5•b5=2b5______ (2)b5+b5=b10______ (3)x5÷x5=0______ (4)(-2a2c)3=-8a5c3______ (5)c•c3=c3______ (6)(-a2)5=-a10.______. |
若ax=3,ay=5,求: (1)ax-y的值; (2)a3x-2y的值. |
下列运算正确的是( )A.a3•a4=x12 | B.(-6a6)÷(-2a2)=3a3 | C.(a-2)2=a2-4 | D.2a-3a=-a |
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