Q4 I of 42 Page 136

Let’s find the L.C.M. of the following algebraic expressions:

3x2-15x + 18, 2x2 + 2x-24, 4x2 + 36x + 80


factors of 3x2-15x + 18

=3x2-9x-6x + 18


=3x(x-3)-6(x-3)


=(3x-6) (x-3)


=3(x-2) (x-3)


Factors of 2x2 + 2x-24


=2(x2 + x-12)


=2(x2 + 4x-3x-12)


=2(x(x + 4)-3(x + 4))


=2(x-3) (x + 4)


Factors of 4x2 + 36x + 80


=4(x2 + 9x + 20)


=4(x2 + 5x + 4x + 20)


=4{x(x + 5) + 4(x + 5)}


=4(x + 5) (x + 4)


LCM is the lowest common multiple, which is the product of all the common factors taken once and the remaining factors as it is.


the LCM of 3x2-15x + 18, 2x2 + 2x-24, 4x2 + 36x + 80 is


12(x-2) (x-3) (x + 4) (x + 5)


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