How do you factor the expression $4 a^2 -a - 5$ ?

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Answer 1 · 2016-03-16T12:39:55

$(4a - 5) ( a +1 )$ is the factorised form of the expression.

$4a^2−a−5$

We can Split the Middle Term of this expression to factorise it.

In this technique, if we have to factorise an expression like $xa^2 + ya + z$ , we need to think of 2 numbers such that:

$N_1*N_2 = x*y = 4*-1 = -4$

AND

$N_1 +N_2 = y= -1$

After trying out a few numbers we get $N_1 = -5$ and $N_2 =4$

$4*-5 = -20$ , and $4+(-5)= -1$

$4a^2−a−5 = 4a^2 + 4a−5a−5$

$= 4a( a +1 ) -5 (a+1)$

$= color(green)((4a - 5) ( a +1 )$

$(4a - 5) ( a +1 )$ is the factorised form of the expression.

How do you factor the expression 4 a^2 -a - 54 a^2 -a - 5?