7+5-7+6-3+4+1-4 bằng mấy ai biết không
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ssh=(100-1):1+1=100
tổng=(100+1)x100:2=5050
vậy 1+2+3+4+5+6+7+8+9+10.......+92+93+94+95+96+97+98+99+100=5050
Số số hạng là: (100-1):1+1=100
Tổng là: (100+1)x100:2=5050
Vậy 1+2+3+4+5+...+96+97+98+99+100=5050
Bài 1:1×2×3×4×5×6×7×8×9×10 bằng mấy? Bài 2:5×5×5×5×5×5×5×5×5×5=3628800
Bài 2:9×9×9×9×9×9×9×9×9×9 = 3486784401 (bạn k cho mình nha)
\(\frac{3}{4}x\frac{4}{5}:\frac{3}{5}x\frac{6}{7}:\frac{1}{7}x\frac{5}{6}\)\(=\)\(\frac{3}{4}x\frac{4}{5}x\frac{5}{3}x\frac{6}{7}x\frac{7}{1}x\frac{5}{6}\)\(=\)\(\frac{3x4x5x6x7x5}{4x5x3x7x1x6}\)\(=\)\(\frac{\left(3\right)x\left(4\right)x\left(5\right)x\left(6\right)x\left(7\right)x5}{\left(3\right)x\left(4\right)x\left(5\right)x\left(6\right)x\left(7\right)x1}\)\(=\)\(\frac{5}{1}\)\(=\)\(5\).
Làm 1,2 câu thôi nhé :(
1)
<=> 4x - 20 - 3x - 21 = 5 + 4
<=> 4x - 3x = 5 + 4 + 20 + 21
<=> x = 50
2)
<=> 20 - 5x + 7x - 14 = -2
<=> 2x = -2 - 20 + 14
<=> 2x = -8
<=> x = -8 : 2
<=> x = -4
Các câu sau tươg tự nha
\(\sqrt{13+\sqrt{48}}=\sqrt{13+\sqrt{4.12}}=\sqrt{13+2\sqrt{12}}=\sqrt{\left(\sqrt{12}+1\right)^2}\)
\(=\sqrt{12}+1=2\sqrt{3}+1\)
\(\Rightarrow\sqrt{5-\sqrt{13+\sqrt{48}}}=\sqrt{5-2\sqrt{3}-1}=\sqrt{4-2\sqrt{3}}=\sqrt{\left(\sqrt{3}-1\right)^2}\)
\(=\sqrt{3}-1\)
\(\Rightarrow\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}=\sqrt{3+\sqrt{3}-1}=\sqrt{2+\sqrt{3}}\)
\(\Rightarrow\sqrt{\dfrac{4+2\sqrt{3}}{2}}=\sqrt{\dfrac{\left(\sqrt{3}+1\right)^2}{2}}=\dfrac{\sqrt{3}+1}{\sqrt{2}}\)
\(\Rightarrow2\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}==2.\dfrac{\sqrt{3}+1}{\sqrt{2}}=\sqrt{6}+\sqrt{2}\)
2) biến đổi khúc sau như câu 1:
\(\Rightarrow\sqrt{6+2\sqrt{5-\sqrt{13+\sqrt{48}}}}=\sqrt{6+2\left(\sqrt{3}-1\right)}=\sqrt{4+2\sqrt{3}}\)
\(=\sqrt{\left(\sqrt{3}+1\right)^2}=\sqrt{3}+1\)
1) Ta có: \(\sqrt{5-\sqrt{13+\sqrt{48}}}=\sqrt{5-\sqrt{13+\sqrt{4.12}}}=\sqrt{5-\sqrt{13+2\sqrt{12}}}\)
\(=\sqrt{5-\sqrt{\left(\sqrt{12}\right)^2+2.\sqrt{12}+1^2}}=\sqrt{5-\sqrt{\left(\sqrt{12}+1\right)^2}}=\sqrt{5-\left|\sqrt{4.3}+1\right|}\)
\(=\sqrt{5-\left(2\sqrt{3}+1\right)}=\sqrt{5-2\sqrt{3}-1}=\sqrt{4-2\sqrt{3}}\)
\(=\sqrt{\left(\sqrt{3}\right)^2-2.\sqrt{3}.1+1^2}=\sqrt{\left(\sqrt{3}-1\right)^2}=\left|\sqrt{3}-1\right|=\sqrt{3}-1\)
\(\Rightarrow2\sqrt{3+\sqrt{5-\sqrt{13+\sqrt{48}}}}=2\sqrt{3+\sqrt{3}-1}=2\sqrt{2+\sqrt{3}}\)
\(=2\sqrt{\dfrac{4+2\sqrt{3}}{2}}=2\sqrt{\dfrac{\left(\sqrt{3}\right)^2+2.\sqrt{3}.1+1^2}{2}}=2\sqrt{\dfrac{\left(\sqrt{3}+1\right)^2}{2}}\)
\(=2.\dfrac{\left|\sqrt{3}+1\right|}{\sqrt{2}}=\sqrt{2}\left(\sqrt{3}+1\right)=\sqrt{6}+\sqrt{2}\)
2) Ta có: \(\sqrt{5-\sqrt{13+\sqrt{48}}}=\sqrt{3}-1\) (như trên)
\(\Rightarrow\sqrt{6+2\sqrt{5-\sqrt{13+\sqrt{48}}}}=\sqrt{6+2\left(\sqrt{3}-1\right)}=\sqrt{4+2\sqrt{3}}\)
\(=\sqrt{\left(\sqrt{3}\right)^2+2.\sqrt{3}.1+1^2}=\sqrt{\left(\sqrt{3}+1\right)^2}=\left|\sqrt{3}+1\right|=\sqrt{3}+1\)
Bằng 10
= 12 - 7 + 6 - 3 + 4 + 1 - 4
= 5 + 6 - 3 + 4 + 1 - 4
= 11 - 3 + 4 + 1 - 4
= 8 + 4 + 1 - 4
= 12 + 1 - 4
= 13 - 4
= 9
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