一种有三题:一:若x(x-1)-(x²-y)=2,求[(x²-y²)/2]-xy的值.二:分解因式:(1/4)(a+b)²+a+b+1 (那个1/4是四分之一)三:分解因式:x²-2x-15
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![一种有三题:一:若x(x-1)-(x²-y)=2,求[(x²-y²)/2]-xy的值.二:分解因式:(1/4)(a+b)²+a+b+1 (那个1/4是四分之一)三:分解因式:x²-2x-15](/uploads/image/z/5257986-42-6.jpg?t=%E4%B8%80%E7%A7%8D%E6%9C%89%E4%B8%89%E9%A2%98%EF%BC%9A%E4%B8%80%EF%BC%9A%E8%8B%A5x%EF%BC%88x-1%EF%BC%89-%EF%BC%88x%26sup2%3B-y%EF%BC%89%3D2%2C%E6%B1%82%5B%EF%BC%88x%26sup2%3B-y%26sup2%3B%EF%BC%89%2F2%5D-xy%E7%9A%84%E5%80%BC.%E4%BA%8C%EF%BC%9A%E5%88%86%E8%A7%A3%E5%9B%A0%E5%BC%8F%EF%BC%9A%EF%BC%881%2F4%EF%BC%89%EF%BC%88a%2Bb%EF%BC%89%26sup2%3B%2Ba%2Bb%2B1+%EF%BC%88%E9%82%A3%E4%B8%AA1%2F4%E6%98%AF%E5%9B%9B%E5%88%86%E4%B9%8B%E4%B8%80%EF%BC%89%E4%B8%89%EF%BC%9A%E5%88%86%E8%A7%A3%E5%9B%A0%E5%BC%8F%EF%BC%9Ax%26sup2%3B-2x-15)
一种有三题:一:若x(x-1)-(x²-y)=2,求[(x²-y²)/2]-xy的值.二:分解因式:(1/4)(a+b)²+a+b+1 (那个1/4是四分之一)三:分解因式:x²-2x-15
一种有三题:
一:若x(x-1)-(x²-y)=2,求[(x²-y²)/2]-xy的值.
二:分解因式:(1/4)(a+b)²+a+b+1 (那个1/4是四分之一)
三:分解因式:x²-2x-15
一种有三题:一:若x(x-1)-(x²-y)=2,求[(x²-y²)/2]-xy的值.二:分解因式:(1/4)(a+b)²+a+b+1 (那个1/4是四分之一)三:分解因式:x²-2x-15
一:由x(x-1)-(x²-y)=2,
得y-x=2,求不出[(x²-y²)/2]-xy的值.
将(x²-y²)改成(x²+y²)就可以算了.
[(x²+y²)/2]-xy
=(x²-2xy+y²)/2,
=(y-x)²/2
=2.
二:(1/4)(a+b)²+a+b+1
=[(1/2)(a+b)]²+2×[(1/2)(a+b)]+1
=[(1/2)(a+b)+1]²(完全平方公式).
三:x²-2x-15
=(x-5)(x+3)[十字相乘法,将-15分解成(-5)×3]
2、1/4[(a+b)²+4(a+b+1)]
=1/4[(a+b)²+4(a+b)+4]
=1/4(a+b+2)²
3、十字相乘
(x-5)(x+3)
2.(1/2(A+B)+1)^2
3.(x-5)(x+3)
one :zhi y-x=2 hou mian mei fan la
two:(1/4)(a+b)²+a+b+1
=[(1/2)(a+b)]²+2×[(1/2)(a+b)]+1
=[(1/2)(a+b)+1]²(完全平方公式)。
three:十字相乘
(x-5)(x+3) zhang wo shi zi xiang cheng gui ze