✔ 最佳答案
Instead of treating them as individual equations, use them as simultaneous equations.
|4x-7| = 5
|-8x+3| = 1
Now to get rid of the absolute value, square both sides of each equation.
(|4x-7|)² = 5 => 16x² - 56x + 49 = 25
(|-8x+3|)² = 1 => 64x² - 48x + 9 = 1
So our two equations are now
16x² - 56x + 49 = 25 => 16x² - 56x + 24 = 0
64x² - 48x + 9 = 1 => 64x² - 48x + 8 = 0
To use these as simlutaneous equations, we need to get the x² values equal, so we multiply the first equation by 4, and leave the second equation the same, giving
64x² - 224x + 96 = 0
64x² - 48x + 8 = 0
Now we subtract the second equation from the first, leaving us with one equation
( 64x² - 64x² = 0, -224x - (-48x) = -176x, 96 - 8 = 88 )
-176x + 88 = 0
-176x = -88
176x = 88
So x can only be equal to 1/2 :-)