先化简再求值 (X²-Y²)-3(2X²-3Y²)其中X=2,Y=-33B²-(A²+B²)-B² ,-2(AB-3A²)+(5AB-A²)其中A=2 B=-3
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![先化简再求值 (X²-Y²)-3(2X²-3Y²)其中X=2,Y=-33B²-(A²+B²)-B² ,-2(AB-3A²)+(5AB-A²)其中A=2 B=-3](/uploads/image/z/1344933-45-3.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%86%8D%E6%B1%82%E5%80%BC+%EF%BC%88X%26%23178%3B-Y%26%23178%3B%EF%BC%89%EF%BC%8D3%EF%BC%882X%26%23178%3B%EF%BC%8D3Y%26%23178%3B%EF%BC%89%E5%85%B6%E4%B8%ADX%EF%BC%9D2%2CY%EF%BC%9D%EF%BC%8D33B%26%23178%3B%EF%BC%8D%EF%BC%88A%26%23178%3B%EF%BC%8BB%26%23178%3B%EF%BC%89%EF%BC%8DB%26%23178%3B%E3%80%80%E3%80%80%E3%80%80%2C%EF%BC%8D2%EF%BC%88AB%EF%BC%8D3A%26%23178%3B%EF%BC%89%EF%BC%8B%EF%BC%885AB%EF%BC%8DA%26%23178%3B%EF%BC%89%E5%85%B6%E4%B8%ADA%EF%BC%9D2%E3%80%80B%EF%BC%9D%EF%BC%8D3)
先化简再求值 (X²-Y²)-3(2X²-3Y²)其中X=2,Y=-33B²-(A²+B²)-B² ,-2(AB-3A²)+(5AB-A²)其中A=2 B=-3
先化简再求值 (X²-Y²)-3(2X²-3Y²)其中X=2,Y=-3
3B²-(A²+B²)-B² ,-2(AB-3A²)+(5AB-A²)其中A=2 B=-3
先化简再求值 (X²-Y²)-3(2X²-3Y²)其中X=2,Y=-33B²-(A²+B²)-B² ,-2(AB-3A²)+(5AB-A²)其中A=2 B=-3
(2)(X²-Y²)-3(2X²-3Y²)
=X²-Y²-6X²+9Y²
=-5X²+8Y²
=-5*2²+8(-3)²
=-20+72
=52
(2) 3B²-(A²+B²)-B²
=3B²-A²-B²-B²
=B²-A²
=2²-(-3)²
=4-9
=-5
(3)-2(AB-3A²)+(5AB-A²)
=-2AB+6A²+5AB-A²
=3AB+5A²
=3*2*(-3)+5*2²
=-18+20
=2