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secondary 4 | A Maths
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How do i solve this? Got a lot of questions recently haha bc exams are coming :(
7 - |3x - 1| = |9 - 27x| + 2 |6x - 2|
The nice thing about modulus expressions is that for a two term expression in the brackets not involving division (addition, subtraction or multiplication), we can swap over the terms without penalty, since the expression remains the same.
7 - |3x - 1| = |27x - 9| + 2 |6x - 2|
Positive constant multipliers of factorisation can also be taken out.
7 - |3x - 1| = 9 * |3x - 1| + 2 * 2 * |3x - 1|
To simplify matters, let u = |3x - 1|.
7 - u = 9u + 4u
7 = 14u
u = 1/2
And there you are. Now we convert back the equation back into x.
|3x - 1| = 1/2
3x - 1 = 1/2 or -1/2
3x = 3/2 or -3/2
x = 1/2 or -1/2
Both solutions are valid since x remains in the modulus brackets and there is no “wild” x running around outside the modulus brackets.
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