Step 1: Rearrange the terms of the quadratic expression into standard form ax2+bx+c.
The given expression is 2+5d−12d2.
Rearranging it gives:
−12d2+5d+2
Step 2: Factor out −1 to make the leading coefficient positive, or factor directly. Let's factor directly by finding two numbers that multiply to a×c=(−12)×2=−24 and add up to b=5.
The two numbers are 8 and −3.
Step 3: Rewrite the middle term 5d using these two numbers.
−12d2+8d−3d+2
Step 4: Group the terms and factor out common factors from each group.
(−12d2+8d)+(−3d+2)
Factor 4d from the first group and −1 from the second group:
4d(−3d+2)−1(3d−2)
To make the binomials identical, we can factor out −4d from the first group instead:
−4d(3d−2)−1(3d−2)
Step 5: Factor out the common binomial (3d−2).
(3d−2)(−4d−1)
This can also be written as (2−3d)(4d+1) by factoring out −1 from the first factor and −1 from the second factor, then multiplying the two −1s to get +1, or by factoring −(12d2−5d−2).
Let's verify the factorization:
(3d−2)(−4d−1)=3d(−4d)+3d(−1)−2(−4d)−2(−1)
=−12d2−3d+8d+2
=−12d2+5d+2
This matches the original expression.
The completely factorised expression is (3d−2)(−4d−1).
That's 2 down. 3 left today — send the next one.