Tính A
A=2.4 + 4.6 + ..... + 98.100
Tính A
A=2.4 + 4.6 + ..... + 98.100
\(A=2.4+4.6+6.8+...+96.98+98.100\)
\(\Rightarrow6A=2.4.6+4.6.8-2.4.6+6.8.10-4.6.8+...+96.98.100-94.96.98+98.100.102-96.98.100\)
\(\Rightarrow6A=\left(2.4.6+4.6.8+6.8.10+...+96.98.100+98.100.102\right)-\left(2.4.6+4.6.8+...+94.96.98+96.98.100\right)\)\(\Rightarrow6A=98.100.102\)
\(\Rightarrow A=\frac{98.100.102}{6}=98.100.17=166600\)
P/s: Ko chắc
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Câu hỏi của Kanzaki Mizuki -toán lớp 6
tính A biết : A= 1.3+3.5+5.7+...+97.99+99.101
A=2.4+4.6+6.8+...+98.100+100.102
A = 1×3+3×5+5×7+...+ 97×99+99×101
6A= 1×3×6+3×5×6+5×7×6+...+97×99×6+99×101×6
6A= 1×3×(5+1)+3×5×(7-1)+5×7×(9-3)+...+97×99×(101-95)+99×101×(103-97)
6A = 1×3×5-1×3+3×5×7-1×3×5+5×7×9-3×5×7+7×9×11-5×7×9+,,,+97×99×101-95×97×99+99×101×103-97×99×101
6A= 1×3+99×101×103
6A= 1029900
A= 171650
Tinh:
a/S=0.2+2.4+4.6+......+98.100
b/ A= 0.2+2.4+4.6+......+ 2n(2n+2)
tinh tổng :
a. S = 0.2 + 2.4 + 4.6 +.......+ 98.100
b. S= 0.2+ 2.4 + 4.6 + .........+ 2n. ( 2n +2 )
Tính
a,B=2.4+4.6+6.8+...+98.100
b,B=3+3.6+6.9+...+96.99
a,6B=2.4.6+4.6.(8-2)+...............+98.100.(102-96)
6B=2.4.6+4.6.8-2.4.6+..............+98.100.102-96.98.100
6B=98.100.102
B=98.100.102:6
B=166600
Tính A
A=2.4 + 4.6 + ..... + 98.100
\(6A=2.4.6+4.6.6+......+98.100.6=2.4.6+4.6.\left(8-2\right)+.....+98.100.\left(102-96\right)=2.4.6+4.6.8-2.4.6+.......+98.100.102-96.98.100=98.100.102=99960000\Rightarrow A=16660000\)
tính P=1/2.4+1/4.6+...+1/98.100
\(2P=\frac{2}{2.4}+\frac{2}{4.6}+...+\frac{2}{98.100}\)
\(2P=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}+...+\frac{1}{98}-\frac{1}{100}\)
\(2P=\frac{1}{2}-\frac{1}{100}\)
=> P =\(\frac{49}{100}:2=\frac{49}{100}\cdot\frac{1}{2}=\frac{49}{200}\)
2.4+4.6+6.8+...+98.100/1.2+2.3+3.4+...+49.50. Tính
\(\frac{2.4+4.6+6.8+...+98.100}{1.2+2.3+3.4+...+49.50}=\frac{4.\left(1.2+2.3+3.4+...+49.50\right)}{1.2+2.3+3.4+...+49.50}=\frac{4}{1}=4\)