Tính hợp lí:
E = (144 x 790) : 72
Tính bằng cách thuận tiện nhất 36 x 5 + 72 x 2 - 216 + 144
\(36\text{×}5+72\text{×}2-216+144\)
\(=36\text{×}5+36\text{×}2\text{×}2-36\text{×}6+36\text{×}4\)
\(=36\text{×}5+36\text{×}4-36\text{×}6+36\text{×}4\)
\(=36\text{×}\left(5+4-6+4\right)=36\text{×}7=252\)
Tính hợp lí:
a ) 2 7 − 3 11 + 5 7 − 8 11 ; b ) 6 21 − 12 44 + 10 14 − 24 33 − 1 c ) − 7 2 + 11 9 − 1 4 + 7 9 ; d ) 1 − − 14 4 + 33 27 − 6 24 + 28 36
tinh nhanh 72 x 19 + 36 x 6 x 10 + 144 x 40 - 72 x 29
`= 72 xx 19 + 36 xx 2 xx3 xx 10 + 72 xx 80 - 72 xx 29`
`= 72 xx(19 + 30 - 29 + 80)`
`= 72 xx 100`
`= 7200`
\(=72.19+36.2.3.10+72.2.40-72.29\)
\(=72.19+72.30+72.80-72.29\)
\(=72.\left(19+30+80-29\right)\)
\(=72.100=7200\)
Tính giá trị của biểu thức:A=72+36nhân 2+24nhân3+18 nhân 4 +12nhân 6+144/ 9,8+8,7+7,6+...+3,2+2,1- 1,2-3,4-...-7,8-8,9. Dấu/nghĩa là 72+36+...++144 trên 9,8+...-8,9
36 x 5 + 72 x 2 - 216 + 144
a, 96 - 7 . ( x + 1) = 144 : 143
b ( 5 . x + 34 ) . 24 = 26 . 72
a) \(96-7\left(x+1\right)=14^4:14^3\)
\(\Rightarrow96-7\left(x+1\right)=14^{4-3}\)
\(\Rightarrow96-7\left(x+1\right)=14\)
\(\Rightarrow7\left(x+1\right)=96-14\)
\(\Rightarrow7\left(x+1\right)=82\)
\(\Rightarrow x+1=\dfrac{82}{7}\)
\(\Rightarrow x=\dfrac{82}{7}-1\)
\(\Rightarrow x=\dfrac{75}{7}\)
b) \(\left(5x+3^4\right)\cdot2^4=2^6\cdot7^2\)
\(\Rightarrow5x\cdot2^4+3^4\cdot2^4=2^6\cdot7^2\)
\(\Rightarrow5x\cdot2^4+6^4=\left(2^3\cdot7\right)^2\)
\(\Rightarrow80x+1296=3136\)
\(\Rightarrow80x=1840\)
\(\Rightarrow x=\dfrac{1840}{80}\)
\(\Rightarrow x=23\)
a: =>96-7(x+1)=14
=>7(x+1)=82
=>x+1=82/7
=>x=75/7
b =>5x+81=2^2*7^2=196
=>5x=115
=>x=23
a) \(96-7\left(x+1\right)=14^4:14^3\\ \Leftrightarrow96-7\left(x+1\right)=14\\ \Leftrightarrow7\left(x+1\right)=82\\ \Leftrightarrow x+1=\dfrac{82}{7}\\ \Leftrightarrow x=\dfrac{75}{7}\)
b) \(\left(5x+3^4\right)\cdot2^4=2^6\cdot7^2\\\Leftrightarrow5x+81=196\\ \Leftrightarrow5x=115\\ \Leftrightarrow x=23 \)
\(\dfrac{1}{72}\) x \(\dfrac{144}{23}\) + \(\dfrac{1}{46}\)
\(\dfrac{1}{72}\) x \(\dfrac{144}{23}\)+ \(\dfrac{1}{46}\)
\(=\dfrac{4}{46}+\dfrac{1}{46}=\dfrac{5}{46}\)
\(\dfrac{1}{72}\times\dfrac{144}{23}+\dfrac{1}{46}=\dfrac{144}{1656}+\dfrac{1}{46}=\dfrac{2}{23}+\dfrac{1}{46}=\dfrac{4}{46}+\dfrac{1}{46}=\dfrac{5}{46}\)
Tính nhanh giáo trị biểu thức 72^2+144*16+16^2-12^2
\(72^2+144\cdot16+16^2-12^2\)
\(=\left(72^2+144\cdot16+16^2\right)-12^2\)
\(=\left(72^2+2\cdot72\cdot16+16^2\right)-12^2\)
\(=\left(72+16\right)^2-12^2\)
\(=88^2-12^2\)
\(=\left(88+12\right)\left(88-12\right)\)
\(=100\cdot76\)
\(=7600\)