作业帮22x-x^2=72念出来就是 22x-x的平方=72 x为两个根 分别是多少
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22x-x^2=72念出来就是 22x-x的平方=72 x为两个根 分别是多少
22x-x^2=72
念出来就是 22x-x的平方=72 x为两个根 分别是多少
22x-x^2=72念出来就是 22x-x的平方=72 x为两个根 分别是多少
22x-x^2=72
x平方-22x+72=0
(x-4)(x-18)=0
x=4或x=18
x² + 22x + 72 = 0
x² + 22x + 72 - 72 = 0 - 72. This is because we want to isolate the variables.
x² + 22x = -72
Take half of the x term and square it. * Because (a+b)² ...
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x² + 22x + 72 = 0
x² + 22x + 72 - 72 = 0 - 72. This is because we want to isolate the variables.
x² + 22x = -72
Take half of the x term and square it. * Because (a+b)² = a² + 2ab + b²
Then add it to both sides.
x² + 22x + 121 = -72+121
x² + 22x + 121 = 49
(x + 11)² = 49
Square root both sides
x + 11 = ±7
x + 11 = 7 and x + 11 = -7
Ans. x = -4, x = -18
收起
（22x-x）*2=72
所以x² + 22x + 121 = 49
(x + 11)² = 49
x + 11 = ±7
x + 11 = 7 and x + 11 = -7
x = -4, x = -18
（X-4)(X-18)=0
X1=4，X2=18