R = speed in still water
r + c = speed with current
r - c = speed against current
3.5(r + c) = 70
r + c = 20
c = 20 - r
4(r + c) = distance from pier to pier
5(r - c) = distance from pier to pier
4(r + c) = 5(r - c)
4(r + 20 - r) = 5(r - 20 + r)
80 = 10r - 100
180 = 10r
18 = r
The speed in still water is 18 km/hour
Answer:
Step-by-step explanation:
the answer is either d or b but i think its d
Complete theh square
isolate x terms
factor out coefient of x^2 term
take 1/2 of 1st degree coefient and square it, add positive and negative inside parnthasees, expand
f(x)=(2x^2+12x)+7
f(x)=2(x^2+6x)+7
6/2=3, 3^2=9
f(x)=2(x^2+6x+9-9)+7
f(x)=2((x+3)^2-9)+7
f(x)=2(x+3)^2-19+7
f(x)=2(x+3)^2-12
Answer: √8
Explanation: x=(5/√8) x (√8 √8)