multiply

Multiply: (7b + 3)(3b – 4)

using the F O I L method

= 7b*3b + 7b*(-4) + 3*3b + 3*(-4)

=21b + 28b +9b -12

=21b +19b-12

Well you are definitely on the right track here, and I appreciate the work you have shown. However, there are a couple problems:

7b*3b should equal 21b². That's because you multiply the 7 and the 3, and also the b with the other b.

7b*(-4) should equal -28b. Probably just a simple mistake of overlooking the negative sign there.

Your other two terms are correct, so the final answer would be:

21b² -28b + 9b - 12
21b² -19b - 12

How about this one

(0.6 - 4)(3a-0.7)

= 0.6*3a + 0.6a*-0.7 + 4*3a + -4*(-0.7)

=1.8a^2 -0.42a -12 +2.8

=1.8a^2 -12.42 +2.8