4-x/7-x/9=0; 4-(9x-7x)/63=0;4 - 2x/63=0,-2x/63=-4; 2x=63*4,2x=252, x=126
a) = (2x - 1 + 3)(2x-1-3) = (2x+2)(2x-4)= 2(x+1)2(x-2)= 4(x+1)(x-2)
b) = (2a+(4a+3))(2a-(4a+3)) = (2a+4a+3)(2a-4a-3)= (6a+3)(-2a-3)= - 3(2a+1)(2a+3)
c) = ((4x-y) + (5x-2y))((4x-y) - (5x-2y)) = (4x-y + 5x-2y)(4x-y - 5x+2y) = (9x-3y)(-x+y) = 3(3x-y)(y-x)
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Y=2x+8
k=2, b=8
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