当代数式x²+3x+5=7时,求代数式3x²+9x-2还有2个(a-2b+3c)²-(a+2b-3c)²已知x+y=4,xy=1,求代数式(x²+1)(y²+1)
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/22 09:27:04
![当代数式x²+3x+5=7时,求代数式3x²+9x-2还有2个(a-2b+3c)²-(a+2b-3c)²已知x+y=4,xy=1,求代数式(x²+1)(y²+1)](/uploads/image/z/1119843-27-3.jpg?t=%E5%BD%93%E4%BB%A3%E6%95%B0%E5%BC%8Fx%26%23178%3B%2B3x%2B5%3D7%E6%97%B6%2C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F3x%26%23178%3B%2B9x-2%E8%BF%98%E6%9C%892%E4%B8%AA%EF%BC%88a-2b%2B3c%EF%BC%89%26%23178%3B-%EF%BC%88a%2B2b-3c%EF%BC%89%26%23178%3B%E5%B7%B2%E7%9F%A5x%2By%3D4%EF%BC%8Cxy%3D1%EF%BC%8C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F%EF%BC%88x%26%23178%3B%2B1%EF%BC%89%EF%BC%88y%26%23178%3B%2B1%EF%BC%89)
当代数式x²+3x+5=7时,求代数式3x²+9x-2还有2个(a-2b+3c)²-(a+2b-3c)²已知x+y=4,xy=1,求代数式(x²+1)(y²+1)
当代数式x²+3x+5=7时,求代数式3x²+9x-2
还有2个
(a-2b+3c)²-(a+2b-3c)²
已知x+y=4,xy=1,求代数式(x²+1)(y²+1)
当代数式x²+3x+5=7时,求代数式3x²+9x-2还有2个(a-2b+3c)²-(a+2b-3c)²已知x+y=4,xy=1,求代数式(x²+1)(y²+1)
1.3X²+9x-2
=3X²+9x+15-17
=3(X²+3x+5)-17
=3*7-17
=4
2.(a-2b+3c)²-(a+2b-3c)²
=[a-(2b-3c)]²-[a+(2b-3c)]²
=-4a(2b-3c)
=-8ab+12ac
3.因为x+y=4,所以(x+y)²=16,x²+2xy+y²=16,又因为xy=1,所以x²+y²=14
(x²+1)(y²+1)
=x²y²+x²+y²+1
=(xy)²+x²+y²+1
=1+14+1
=16