✔ 最佳答案
You can either put them in the form of:
ax² + bx + c = 0
and factor if you can, or use quadratic equation, or in the form of:
x² + bx = c
and complete the square.
I'll complete the square on the first one:
2x² + 4x = -3
divide all by 2:
x² + 2x = -3/2
Half the coefficient of the "x" and square it, then add that to both sides. In this case, it's 1:
x² + 2x + 1 = -3/2 + 1
simplify:
(x + 1)² = -1/2
x + 1 = ± √(-1/2)
x = -1 ±√(-1/2)
Now simplify to get the fraction and negative out of the radical:
x = -1 ±√(-1/2)
x = -1 ± i/√(2)
x = -1 ± i√(2)/2
For #2: I'll factor:
2x² - 32x = 0
2x(x - 16) = 0
Since the product of anything and 0 is 0, I'll set both of these to 0 and solve for x:
2x = 0
x = 0
x - 16 = 0
x = 16
x = 0 and 16.
#3, put it into a standard form first:
2x(x - 4) = 3(1 - x)
2x² - 8x = 3 - 3x
2x² - 5x - 3 = 0
I'll use quadratic formula here:
x = [-b ± √(b² - 4ac)] / 2a
x = [-(-5) ± √((-5)² - 4(2)(-3))] / 2(2)
x = [5 ± √(25 + 24)] / 4
x = [5 ± √(49)] / 4
x = [5 ± 7] / 4
x = -2/4 and 12/4
x = -1/2 and 3
Since that came out as rational numbers, this could have been factored, but as I said, either method would work.