\(B=\frac{780^2-220^2}{125^2+150.125+75^2}\)\(=\frac{\left(780+220\right).\left(780-220\right)}{\left(125+75\right)^2}\)\(=\frac{1000.560}{200^2}\)\(=\frac{560000}{40000}=14\)
Tính nhanh :
A=100^2+98^2+96^2+....+2^2 - 99^2-97^2-95^2-....-1^2
B= 780^2-220^2/125^2+75^2+150.125
\(\left(780^2-220^2\right):\left(125^2+150.125+75^2\right)\)
Tính nhanh:
7802 - 2202
1252 + 150.125 + 752
Tính nhanh :
a) ( 202 + 182 + 162 + ... + 42 ) - ( 192 + 172 + 152+ ... + 12 )
b) \(\frac{780^2-220^2}{125^2+150.125+75^2}\)
Tính nhanh, dùng hằng đẳng thức thứ 1;2;3
a) 1272 + 146 . 127 + 732
b) 98 . 28 - (184 - 1)(184 + 1)
c) \(\frac{780^2-220^2}{125^2+150.125+75^2}\)
Tính nhanh
a,\(A=100^2-99^2+98^2-97^2+...+2^2-1^2\)
b,\(B=\left(20^2+18^2+...+2^2\right)-\left(19^2+17^2+....+3^2+1^2\right)\)
c,\(C=\frac{780^2-220^2}{125^2+150.125+75^2}\)
d,\(D=2.\left(a+5\right).\left(a+4\right)-\left(a+5\right)^2-\left(a^2-9a-17\right)\)với a=99
tính nhanh
a)1272+146.127+732
b)98.28-(184-1)(184+1)
c)1802-2202/1252+150.125+752
Bài 1: Rút gọn: (3+1)(32+1)(34+1)(38+1)(316+1)(332+1)
Bài 2: So sánh: \(\frac{x-y}{x+y}\)và \(\frac{x^2-y^2}{x^2+y^2}\)với x>y>0
Bài 3: Tính nhanh:
1, \(\frac{780^2-220^2}{125^2+150.125+75}\)
2, \(\text{(20^2 + 18^2 + 16^2 + ... + 4^2 + 2^2)-(19^2 + 17^2 + 15^2 + ... + 3^2 + 1^2)}\)
\(I\)Tính nhanh
\(a.127^2+146.127+73^2\)
\(b.9^8.2^8\left(18^4-1\right)\left(18^4+1\right)\)
\(c.100^2-99^2+98^2-97^2+...+2^2-1^2\)
\(d.\frac{780^2-220^2}{125^2+150.125+75^2}\)
\(II.\)Rút gọn các biểu thức
\(x^2\left(x+4\right)\left(x-4\right)-\left(x^2+1\right)\left(x^2-1\right)\)
\(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2+2\right)\left(y^2-2\right)\)
\(5\left(2x-1\right)^2+4\left(x-1\right)\left(x+3\right)-2\left(5-3x\right)^2\)