Rút gọn
\(A=\frac{a^2.a^7.b^2.c^8}{a^5.b^3.\left(-c\right)^4}\)
B=\(\left(\frac{3}{7}\right)^{5.}\frac{\left(25\right)^4.7^5}{15^4.20^2}\)
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\(B=\left(\frac{3}{7}\right)^5.\frac{5^8.7^5}{3^4.5^4.2^4.5^2}\)
\(B=\frac{3^5.5^8.7^5}{3^4.5^6.2^4.7^5}\)
\(B=\frac{3.5^2}{2^4}\)
\(B=\frac{75}{16}\)
Bài làm
\(a,\left(\frac{3}{7}+\frac{1}{2}\right)^2\)
\(=\left(\frac{3}{7}\right)^2+\left(\frac{1}{2}\right)^2\)
\(=\frac{9}{49}+\frac{1}{4}\)
\(=\frac{36}{196}+\frac{49}{196}\)
\(=\frac{85}{196}\)
\(b,\left(\frac{3}{4}-\frac{5}{6}\right)^2\)
\(=\left(-\frac{1}{12}\right)^2\)
\(=\frac{1}{144}\)
\(c,\frac{5^4.20^4}{25^5.4^5}\)
\(=\frac{5^4.\left(5.4\right)^4}{\left(5.5\right)^5.4^5}\)
\(=\frac{5^4.5^4.4^4}{5^5.5^5.4^5}\)
\(=\frac{1}{5.5.4}\)
\(=\frac{1}{100}\)
~ Check đúng cho minh nha. ~
# Học tốt #
\(a,\left(\frac{3}{7}+\frac{1}{2}\right)^2\)
\(< =>\left(\frac{6}{14}+\frac{7}{14}\right)^2\)
\(< =>\left(\frac{13}{14}\right)^2\)
\(< =>\frac{169}{196}\)
\(b,\left(\frac{3}{4}-\frac{5}{6}\right)^2\)
\(< =>\left(\frac{9}{12}-\frac{10}{12}\right)^2\)
\(< =>\left(\frac{-1}{12}\right)^2\)
\(< =>\frac{-1}{144}\)
\(c,\frac{5^4\cdot20^4}{25^5\cdot4^5}\)
\(< =>\frac{25^2\cdot\left(4\right)^4\cdot\left(5\right)^4}{25^5\cdot4^5}\)
\(< =>\frac{1\cdot1\cdot\left(5\right)^4}{25^3\cdot4}\)
\(< =>\frac{1\cdot25^2}{25^3\cdot4}\)
\(< =>\frac{1}{25\cdot4}\)
\(< =>\frac{1}{100}\)
a) \(A=\left[\left(\frac{1}{5}\right)^2\right]^{\frac{-3}{2}}-\left[2^{-3}\right]^{\frac{-2}{3}}=5^3-2^2=121\)
b) \(B=6^2+\left[\left(\frac{1}{5}\right)^{\frac{3}{4}}\right]^{-4}=6^2+5^3=161\)
c) \(C=\frac{a^{\sqrt{5}+3}.a^{\sqrt{5}\left(\sqrt{5}-1\right)}}{\left(a^{2\sqrt{2}-1}\right)^{2\sqrt{2}+1}}=\frac{a^{\sqrt{5}+3}.a^{5-\sqrt{5}}}{a^{\left(2\sqrt{2}\right)^2-1^2}}\)
\(=\frac{a^{\sqrt{5}+3+5-\sqrt{5}}}{a^{8-1}}=\frac{a^8}{a^7}=a\)
d) \(D=\left(a^{\frac{1}{2}}-b^{\frac{1}{2}}\right)^2:\left(b-2b\sqrt{\frac{b}{a}}+\frac{b^2}{a}\right)\)
\(=\left(\sqrt{a}-\sqrt{b}\right)^2:b\left[1-2\sqrt{\frac{b}{a}}+\left(\sqrt{\frac{b}{a}}\right)^2\right]\)
\(=\left(\sqrt{a}-\sqrt{b}\right)^2:b\left(1-\sqrt{b}a\right)^2\)
f) \(\frac{3^3.\left(0,5\right)^5}{\left(1,5\right)^4}=\frac{3^3.\left(0,5\right)^5}{\left[3.\left(0,5\right)\right]^4}=\frac{3^3.\left(0,5\right)^5}{3^4.\left(0,5\right)^4}=\frac{0,5}{3}=\frac{1}{6}\)
b) \(\frac{2^3+3.2^6-4^3}{2^3+3^2}=\frac{2^3.\left(1+3.2^3-2^3\right)}{2^3+3^2}=\frac{2^3.17}{17}=2^3=8\)
Các phần còn lại tương tự, bạn tự làm nhé !
(*) Lưu ý ở những bài rút gọn có chứa lũy thừa thì bạn đưa số đó về số nguyên tố rồi thực hiện như bình thường .
VD : \(4^3=\left(2^2\right)^3=2^6\) ( đưa về số nguyên tố là 2 )
\(6^3=\left(2.3\right)^3=2^3.3^3\) ( đưa về tích hai số nguyên tố )
Bài 1:
d)
= \(\frac{-5}{9}\left(\frac{6}{13}+\frac{7}{13}\right)+\frac{5}{23}.\frac{7}{9}\)
= \(\frac{-5}{9}.1+\frac{35}{207}\)
= \(\frac{-80}{207}\)
Bài 2:
a) 20%x + 0,4x = 4,5
x( 20% + 0,4 ) = 4,5
x. 0,6 = 4,5
x = 4,5 : 0,6
x = 7,5
ý B hình như mk giải rồi thì phải
\(A=\frac{a^2.a^7.b^2.c^8}{a^5.b^3.\left(-c\right)^4}=\frac{a^9.b^2.c^8}{a^5.b^3.c^4}=\frac{a^4.c^4}{b}\)
\(B=\left(\frac{3}{7}\right)^5.\frac{\left(25\right)^4.7^5}{15^4.20^2}=\frac{3^5.\left(5^2\right)^4.7^5}{7^5.\left(3.5\right)^4.\left(4.5\right)^2}=\frac{3^5.5^8.7^5}{7^5.3^4.5^4.4^2.5^2}\)
\(=\frac{3^5.5^8.7^5}{7^5.3^4.5^6.4^2}=\frac{3.5^2}{4^2}=\frac{75}{16}\)