12-0.2^2 000 x 5^2 001 =
A.-5^4 001
B.-5
C.-1
D.-0.2
13If 2^x-1 =1/16 , then the value of x is
A.-4.
B.-3.
C. .-1/4
D.5.
17If 3^m -2 = 5 and 9^n = 10, then the value of 3^m + 2n is
A.55.
B.150.
C.300.
D.450.
19the following expressions must be correct?
3y^4-2y^3 = y
F.3 Laws of Integral Indices
2010-09-19 8:21 pm
回答 (1)
2010-09-19 8:40 pm
✔ 最佳答案
12)-0.2^2000 x 5^2001
=-(1/5)^2000 x 5^2001
=-(5^(-1))^2000 x 5^2001
=-(5^(-2000)) x 5^2001
=-(5^(-2000+2001))
=-5
Ans: B
13)
2^(x-1)=1/16
2^(x-1)=1/2^4
2^(x-1)=2^(-4)
x-1=-4
x=-3
Ans: B
17)
3^(m-2) = 5 => 3^m*3^(-2)=5 => 3^m*(1/9)=5 => 3^m=45
9^n=10 =>3^(2n)=10
3^(m+2n)=3^m*3^2n=45*10=450
Ans: D
19)
For instance, take y=2
3*2^4-2*2^3=32=/=2
So, the expression is not always correct.
收錄日期: 2021-04-22 00:51:14
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