Solve for x and y if 5x−y = 625 and 32x × 3y = 243.

Question

Hence, evaluate

35x/7^(−2y) × 5^(−3y)

Need help for solving x and y, thanks!

Answer 1

5x−y = 625 -----> y = 5x-625

sub into the 2nd equation:
32x × 3y = 243 ----- divide both sides by 3
32xy = 81
32x(5x-625) = 81
160x^2 - 20000x - 81 = 0
yuk
this is not going nicely ...
use your calculator and the quadratic formula to find
x, then y

let's work on the other part:
35x/7^(−2y) × 5^(−3y)
I will assume you meant:
(35x/7)^(−2y) × 5^(−3y)
= (5x)^(-2y) × 5^(-3y)
= 5^(-2y) × x^(-2y) × 5^(-3y)
= 5^(-5y) × x^(-2y)

sub in the x and y from above.

looks quite messy, check your typing, I already made one assumption.