计算 15²-4×2.5²
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计算 15²-4×2.5²
计算 15²-4×2.5²
计算 15²-4×2.5²
15²-4×2.5²
=15^2-5^2
=(15-5)(15+5)
=10*20
=200
200
15²-4×2.5²
=225-4×2.5×2.5
=225-10×2.5
=225-25
=200
15²-4×2.5²
=(15+5)(15-5)
=20x10
=200
15²-4×2.5²=225-4x6.25=225-25=200
15²-4×2.5²
= (15 + 2×2.5)*(15 - 2×2.5)
= (15 + 5)*(15 - 5)
= 20 * 10
= 200