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\(48^2-42^2+64-52^2\)
\(=\left(48^2-52^2\right)-\left(42^2-64\right)\)
\(=\left(48^2-52^2\right)-\left(42^2-8^2\right)\)
\(=\left(48-52\right)\left(48+52\right)-\left(42+8\right)\left(42-8\right)\)
\(=-4\cdot100-50\cdot34\)
\(=-8\cdot50-50\cdot34\)
\(=-50\cdot\left(8+34\right)\)
\(=-50\cdot42\)
\(=-2100\)
482 + 522 + 52.96
= 482 + 2.48.52 + 522
= ( 48 + 52 )2
= 1002 = 10 000
\(52^2+2.52.48+48^2=\left(52+48\right)^2\)
\(=100^2\)
\(=10000\)
Bài 13:
a) \(501^2\)
\(=\left(500+1\right)^2\)
\(=500^2+2\cdot500\cdot1+1^2\)
\(=250000+1000+1\)
\(=251001\)
b) \(88^2+24\cdot88+12^2\)
\(=88^2+2\cdot12\cdot88+12^2\)
\(=\left(88+12\right)^2\)
\(=100^2\)
\(=10000\)
c) \(52\cdot48\)
\(=\left(50+2\right)\left(50-2\right)\)
\(=50^2-2^2\)
\(=2500-4\)
\(=2496\)
Bài 14:
a) \(P=\left(2x-1\right)\left(4x^2+2x+1\right)+\left(x+1\right)\left(x^2-x+1\right)\)
\(P=\left(2x\right)^3-1+x^3+1\)
\(P=8x^3+x^3\)
\(P=9x^3\)
b) \(Q=\left(x-y\right)\left(x^2+xy+y^2\right)-\left(x+y\right)\left(x^2-xy+y^2\right)+2y^3\)
\(Q=x^3-y^3-x^3-y^3+2y^3\)
\(Q=-2y^3+2y^3\)
\(Q=0\)
a: Ta có: \(A=\dfrac{35^3+13^3}{48}-35\cdot13\)
\(=35^2-35\cdot13+13^2-35\cdot13\)
\(=\left(35-13\right)^2\)
\(=22^2=484\)
b: Ta có: \(B=\dfrac{68^3-52^3}{16}+68\cdot52\)
\(=68^2+68\cdot52+52^2+68\cdot52\)
\(=\left(68+52\right)^2=14400\)
52.143 -52.39 -8.26 =52.143-52.39-4.52 =52.(143-39-4) =52. 100 =5200 chúc bạn thành công !
52 . 143 - 52 . 39 - 8 . 26
= 52 . 143 - 52 . 39 - 4 . 52
= 52 . (143 - 39 - 4)
= 52 . 100 = 5200