2. จงหาผลลัพธ์
1) \(\mathtt{[(-2)^4 \times (-2)^3 \times (-2)^0] \div (-2)^5}\)
วิธีทำ
\(\mathtt{[(-2)^4 \times (-2)^3 \times (-2)^0] \div (-2)^5}\) = \(\mathtt{[(-2)^{4+3+0}] \div (-2)^5}\)
= \(\mathtt{(-2)^7 \div (-2)^5}\)
= \(\mathtt{[(-2)^{7-5}}\)
= \(\mathtt{[(-2)^2}\)
= 4
ตอบ 4
2) \(\mathtt{(3^5 \times 3^{-2} \times 3^2) \div 3^4}\)
วิธีทำ
\(\mathtt{(3^5 \times 3^{-2} \times 3^2) \div 3^4}\) = \(\mathtt{(3^{5+(-2)+2}) \div 3^4}\)
= \(\mathtt{3^5 \div 3^4}\)
= \(\mathtt{3^{5-4}}\)
= \(\mathtt{3^1}\)
= \(\mathtt{3}\)
ตอบ 3
3) \(\mathtt{[49 \times (-7)^3] \div (-7)^5}\)
วิธีทำ
\(\mathtt{[49 \times (-7)^3] \div (-7)^5}\) = \(\mathtt{[(-7)^2 \times (-7)^3] \div (-7)^5}\)
= \(\mathtt{(-7)^{2+3} \div (-7)^5}\)
= \(\mathtt{(-7)^5 \div (-7)^5}\)
= \(\mathtt{(-7)^{5-5}}\)
= \(\mathtt{(-7)^0}\)
= \(\mathtt{1}\)
ตอบ 1
4) \(\mathtt{(6 \times 10^{-2}) \div (9 \times 10^3)}\)
วิธีทำ
\(\mathtt{(6 \times 10^{-2}) \div (9 \times 10^3)}\) = \(\mathtt{\frac{6 \times 10^{-2}}{9 \times 10^{3}}}\)
= \(\mathtt{\frac{2}{3} \times 10^{(-2)-3}}\)
= \(\mathtt{\frac{2}{3} \times 10^{-5}}\)
ตอบ \(\mathtt{\frac{2}{3} \times 10^{-5}}\)
5) \(\mathtt{(2.4 \times 10^{-3}) \div (8 \times 10^5)}\)
วิธีทำ
\(\mathtt{(2.4 \times 10^{-3}) \div (8 \times 10^5)}\) = \(\mathtt{\frac{2.4 \times 10^{-3}}{8 \times 10^{5}}}\)
= \(\mathtt{0.3 \times 10^{(-3)-5}}\)
= \(\mathtt{3
\times 10^{-1} \times 10^{-8}}\)
= \(\mathtt{3 \times 10^{(-1)+(-8)}}\)
= \(\mathtt{3 \times 10^{(-9)}}\)
ตอบ \(\mathtt{3 \times 10^{(-9)}}\)
6) \(\mathtt{(4a^5b^0) \div (2a^2b)}\) เมื่อ \(\mathtt{a \ne 0}\) และ \(\mathtt{b \ne 0}\)
วิธีทำ
\(\mathtt{(4a^5b^0) \div (2a^2b)}\) = \(\mathtt{\frac{4a^5b^0}{2a^2b}}\)
= \(\mathtt{\frac{4}{2} a^{5-2} b^{0-1}}\)
= \(\mathtt{2a^3 b^{-1}}\)
= \(\mathtt{\frac{2a^3}{b}}\)
ตอบ \(\mathtt{\frac{2a^3}{b}}\) เมื่อ \(\mathtt{a \ne 0}\) และ \(\mathtt{b \ne 0}\)
7) \(\mathtt{(5^{4n} \times 5^{5n}) \div 5^{4n}}\) เมื่อ n เป็นจำนวนเต็มบวก
วิธีทำ
\(\mathtt{(5^{4n} \times 5^{5n}) \div 5^{4n}}\) = \(\mathtt{5^{4n+5n} \div 5^{4n}}\)
= \(\mathtt{5^{9n} \div 5^{4n}}\)
=
\(\mathtt{5^{9n-4n}}\)
= \(\mathtt{5^{5n}}\)
ตอบ \(\mathtt{5^{5n}}\)