calculus
posted by gen .
if y1=x^2+3x1 and y2=x5,
find: a. y1+y2
b. y1y2
c. y1(y2)

y1 = x^2 + 3x  1
y2 = x  5
for y1  y2, combine similar terms,, for terms with same variables, add their numerical coefficients (number before the variable) and copy the variable:
x^2 + 3x  1 (x  5)
x^2 + 3x  1  x + 5
x^2 + 3x  x  1 + 5 *i just rearrange the terms*
x^2 + 2x + 4
for y1(y2), distribute each term:
(x^2 + 3x  1)(x  5)
to distribute, multiply x^2 by x plus x^2 times 5, plus 3x times x plus 3x times 5, and so on:
(x^2)*x + (5)x^2 + 3x^2  15x  x + 5
now simplify this by combining similar terms. 
Alright. a. y1+y2 should be set up as follows:
(x^2+3x1)+(x5), which equates to
x^2+4x6
You just combine the like terms.
b. (x^2+3x1)(x5)
For this one you need to distribute the negative, to get x^2+3x1x+5, then combine like terms.
c. (x5)(x^2+3x1)= x^3+3x^2x5x^215x+5. Combine like terms.