✔ 最佳答案
1)
盈利 / 成本 * 100% = 盈利百分比
90(y - 10) / [ (10)(100) ] * 100% = 50%
90(y - 10) / 1000 = 0.5
y = 140/9 = 15.5555....
每件T恤的最低售價為 16 元
2)
√a√a√a√a
= (√a)^4
= a^2
3)
[ x^ (-1) - y^( -1) ] / [ x^(-2) - y^(-2) ]
= [ (y - x) / (xy) ] / [ (y^2 - x^2) / (x^2 y^2) ]
= [ (y - x)(x^2 y^2) ] / [ (y^2 - x^2)(xy) ]
= [ (y - x)(xy) ] / [ (y - x)(y + x) ]
= (xy) / (y + x)
留意 d 括號點用法,唔加括號個意思相差好大
4)
[ b^n - b^(n+3) ] / b^n
= [ b^n - (b^n)(b^3) ] / b^n
= (b^n)(1 - b^3) / b^n
= 1 - b^3
5)
[ 3^(n+1) - 2 * 3^n ] / 3^(n-1)
= [ 3 * 3^n - 2 * 3^n ] / 3^(n-1)
= 3^n / 3^(n-1)
= 3
6)
√49000000 * √64 * 10^(-4)
= 7000 * 8 / 10000
= 28/5
= 5.6
125 * 10^(-5) + 0.4 * 10^(-4)
= 125/100000 + 0.4/10000
= 125/100000 + 4/100000
= 129/100000
= 1.29 * 10^(-3)
咁多條, 好辛苦啊
